The AFC Competitions Committee recommended a new format for the AFC Cup starting from 2017 which was played in the AFC's five zones: West Asia, Central Asia, South Asia, ASEAN, and East Asia, with the winner of the West Asia Zone and the winner of an inter-zone play-off between the other four zones playing in the final, hosted on a rotational basis at venues in the East and West. The 46 AFC member associations (excluding the associate member Northern Mariana Islands) were ranked based on their national team's and clubs' performance over the last four years in AFC competitions, with the allocation of slots for the 2017 and 2018 editions of the AFC club competitions determined by the 2016 AFC rankings (Entry Manual Article 2.2):
All associations which do not receive direct slots in the AFC Champions League group stage are eligible to enter the AFC Cup.
In each zone, the number of groups in the group stage is determined based on the number of entries, with the number of slots filled through play-offs same as the number of groups: In the West Asia Zone and the ASEAN Zone, there are three groups in the group stage, including a total of 9 direct slots, with the 3 remaining slots filled through play-offs. In the Central Asia Zone, the South Asia Zone, and the East Asia Zone, there was one group in the group stage, including a total of 3 direct slots, with the 1 remaining slot filled through play-offs.
The top associations participating in the AFC Cup in each zone as per the AFC rankings got at least one direct slot in the group stage (including losers of the AFC Champions League qualifying play-offs), while the remaining associations get only play-off slots: For the West Asia Zone and the ASEAN zone: The associations ranked 1st to 3rd each got two direct slots. The associations ranked 4th to 6th each got one direct slot and one play-off slot. The associations ranked 7th or below each got one play-off slot. For the Central Asia Zone, the South Asia Zone, and the East Asia zone: The associations ranked 1st to 3rd each got one direct slot and one play-off slot. The associations ranked 4th or below each got one play-off slot.
The maximum number of slots for each association was one-third of the total number of eligible teams in the top division.
If any association gives up its direct slots, they were redistributed to the highest eligible association, with each association limited to a maximum of two direct slots.
If any association gives up its play-off slots, they were annulled and not redistributed to any other association.
If the number of teams in the play-offs in any zone was fewer than twice the number of group stage slots filled through play-offs, the play-off teams of the highest eligible associations were given byes to the group stage.
For the 2018 AFC Cup, the associations were allocated slots according to their association ranking published on 30 November 2016, which took into account their performance in the AFC Champions League and the AFC Cup, as well as their national team's FIFA World Rankings between 2013 and 2016.
In the qualifying play-offs, each tie was played on a home-and-away two-legged basis. The away goals rule, extra time (away goals do not apply in extra time) and penalty shoot-out were used to decide the winner if necessary (Regulations Article 9.3). The five winners of the play-off round advanced to the group stage to join the 31 direct entrants.
The bracket of the qualifying play-offs for each zone was determined by the AFC based on the association ranking of each team, with the team from the higher-ranked association hosting the second leg.
The draw for the group stage was held on 6 December 2017, 14:00 MYT (UTC+8), at the AFC House in Kuala Lumpur, Malaysia. The 36 teams were drawn into nine groups of four: three groups each in the West Asia Zone (Groups A–C) and the ASEAN Zone (Groups F–H), and one group each in the Central Asia Zone (Group D), the South Asia Zone (Group E), and the East Asia Zone (Group I). Teams from the same association in the West Asia Zone and ASEAN Zone could not be drawn into the same group.
In the group stage, each group was played on a home-and-away round-robin basis. The following teams advanced to the knockout stage:
The winners of each group and the best runners-up in the West Asia Zone and the ASEAN Zone advanced to the Zonal semi-finals.
The winners of each group in the Central Asia Zone, the South Asia Zone, and the East Asia Zone advanced to the Inter-zone play-off semi-finals.
Tiebreakers
The teams were ranked according to points (3 points for a win, 1 point for a draw, 0 points for a loss). If tied on points, tiebreakers were applied in the following order (Regulations Article 10.5): Points in head-to-head matches among tied teams; Goal difference in head-to-head matches among tied teams; Goals scored in head-to-head matches among tied teams; Away goals scored in head-to-head matches among tied teams; If more than two teams are tied, and after applying all head-to-head criteria above, a subset of teams are still tied, all head-to-head criteria above are reapplied exclusively to this subset of teams; Goal difference in all group matches; Goals scored in all group matches; Penalty shoot-out if only two teams are tied and they met in the last round of the group; Disciplinary points (yellow card = 1 point, red card as a result of two yellow cards = 3 points, direct red card = 3 points, yellow card followed by direct red card = 4 points); Team from the higher-ranked association.
In the knockout stage, the 11 teams played a single-elimination tournament. Each tie was played on a home-and-away two-legged basis, except the final which was played as a single match. The away goals rule (for two-legged ties), extra time (away goals do not apply in extra time) and penalty shoot-out were used to decide the winner if necessary (Regulations Article 11.3).
Bracket
The bracket was decided after the draw for the Zonal finals and the Inter-zone play-off semi-finals, which was held on 23 May 2018, 15:00 MYT (UTC+8), at the AFC House in Kuala Lumpur, Malaysia.
In the Zonal semi-finals, the four qualified teams from the West Asia Zone (Groups A–C) played in two ties, and the four qualified teams from the ASEAN Zone (Groups F–H) played in two ties, with the matchups and order of legs determined by the group stage draw and the identity of the best runners-up.
The draw for the Zonal finals was held on 23 May 2018. In the Zonal finals, the two winners of West Asia Zonal semi-finals played each other, and the two winners of ASEAN Zonal semi-finals played each other, with the order of legs decided by draw. The winners of the West Asia Zonal final advanced to the final, while the winners of the ASEAN Zonal final advanced to the Inter-zone play-off semi-finals.
The draw for the Inter-zone play-off semi-finals was held on 23 May 2018. In the Inter-zone play-off semi-finals, the four zonal winners other than the West Asia Zone played in two ties, i.e., the winners of the Central Asia Zone (Group D), the winners of the South Asia Zone (Group E), the winners of the East Asia Zone (Group I), and the winners of the ASEAN Zonal final (whose identity was not known at the time of the draw), with the matchups and order of legs decided by draw, without any seeding.
In the Inter-zone play-off final, the two winners of the Inter-zone play-off semi-finals played each other, with the order of legs determined by the Inter-zone play-off semi-final draw. The winners of the Inter-zone play-off final advanced to the final.
In the final, the winners of the West Asia Zonal final and the winners of the Inter-zone play-off final played each other, with the host team (winners of the West Asia Zonal final) alternated from the previous season's final.