This paper systematically identifies plays in the Triassic Yanchang Formation of the Mesozoic in Ordos Basin.The play division is mainly based on the play definition and the following characteristics of target beds:(1)distributions of source rocks and sandstone reservoirs;(2)distributions of structures and paleo-structures

main faults and carrier systems;(3)distributions of main source rocks for each play;(4)distribution of seals especially regional seals for each play.In addition

the distribution of known structural traps and other possible structural traps as well as the preservation of petroleum system are also considered to identify play.Six plays were identified in the Triassic Yanchang Formation in Ordos Basin:MemberⅩto Member Ⅶ play

Member Ⅶ to Member Ⅴ play

Member Ⅶ to Member Ⅳ+Ⅴplay

upper of Member Ⅳ+Ⅴ to Member Ⅲ play

Member Ⅳ+Ⅴ to Member Ⅱ play and Member Ⅳ to MemberⅠ play.According to the analysis of source rocks

reservoirs and cap rocks in different plays

the Mesozoic plays are mainly distributed in the northwest and southeast and southwest parts of Yishan slope and the south part of Tianhuan depression.