Abstract: After many years of exploration , the hydrocarbon distribution characteristics of the second member of Dongying formation appear in dilution phenomenon with good shows , thick thickness and small reserves in the south of Liaozhong sag.Based on the analysis of lateral sealing of faults , hydrocarbon is difficult to accumulate in huge scale because of the bad availability of traps.According to the occurrences of fluid inclusions , GOI value Statistics , the microscopic fluorescence characteristics and microthermometric statistics , combined with the buried history-geothermal evolution history of the wells , there are two periods of hydrocarbon accumulation in Dong 2 Member in the south of Liaozhong sag.The first period was nearly from9.0 Ma to 5.1 Ma , which occurred in the early of Minghuazhen stage.The second period was nearly from4.0 Ma to 1.3 Ma , which occurred in the end of Minghuazhen stage.Based on the analysis of fault activities , It had experienced a strong tectonic activity in 5.1 Ma ago which occurred in the middle of Minghuazhen stage. Therefore , paleo-reservoirs had been adjusted because of the much more juxtaposition between the Dong 2 member reservoir and the Guantao formation , and the hydrocarbon distribution of Dong 2 member was in dilution phenomenon. Hydrocarbon was migrated to the shallow strata along the faults and accumulated in huge scale.Therefore , the Neogene formation is the main oil-gas exploration strata in the south of Liaozhong sag.