The Dongpu sag locates at the most southern part of the Bohaiwan Basin, there are 4 big sets of the gypsolith rhythmic formations. The reservoir exploration and development practices show that the hydrocarbon accumulation and distribution are closely related to the gypsolith sedimentary in the basin. Based on the principles of sedimentology, structural geology, reservoir geology, geochemistry and previous research and achievements，the controlling factors of the gypsolith distribution was studied using core data, well logging,geophysics and experiment data. It is indicated that synsedimentary faults control the local distribution and sedimentary thickness of the gypsolith. Additionally, the palaeotopography and ancient sources direction control and affect the planar distribution and pattern.The gypsolith sedimentary plays an important role in the formation of abnormal pressure, hydrocarbon lateral block and even hydrocarbon generation, migration and accumulation. Thus, the research achievements provide guidance for the further subtle reservoir exploration, progressive exploration and development, and also exploration in the similar gypsolith-bearing basin.