Abstract: Chengdao area is located in the southern part of Chengbei lower convex of Bohai Bay basin，China．This area contains stratigraphic sequences of almost all ages from Archaean to Tertiary. The structure style shows the characteristics of dyadic structures，and belongs to a typical burial hill-drape anticline Petroleum exploration in the area demonstrates that Chengdao area itself is weak in hydrocarbon generation and the hydrocarbon in the pool came from surrounding depressions including Chengbei depression，Shanan depression，Bozhong depression an d Zhuangdong depression．The hydrocarbon accumulation system in the area is complex，with more than one source rocks，and multiple stages of migration and accumulation．Based on various fundamental geological factors and processes that dominate the hydrocarbon formation and accumulation，the Chengdao composite petroleum system is identified．Four hierarchy levels of the composite petroleum system is subdivided and described，which include 1 composite petroleum system,3 petroleum systems,12 sub-systems and 48(12×4)4th order systems.