Abstract: Based on the analysis results of condensate oil and gas components, biomarkers, stable carbon isotopes and fluid inclusions, compressively using mulitple research methods of petroleum geochemistry, this paper determines the characteristics and genisis of condensate oil and gas and explores the oil-gas formation mechanism in Bozhong19-6 structure, southwestern Bozhong sag, Bohai Bay Basin. The results show that the condensate oil has physical properties of low density, low viscosity, low colloid and asphaltene, high wax and high freezing point. In the condensate oil, n-alkanes are mainly composed of medium and high carbon components, and light hydrocarbon components are dominated by the n-octane, n-heptane and methylcyclohexane with the same contents. The condensate oil is the product of mature source rocks in Member 3 of Shahejie Formation. The natural gas is mainly composed of hydrocarbon gas with low content of non-hydrocarbon gas and derived from the cracking of humic-type source rocks in Member 3 of Shahejie Formation. The Bozhong19-6 structure has experienced multi-stage continuous charging of heavy oil, light oil, condensate oil or gas, and natural gas since 12Ma. The phase-controlled miscibility is the main formation mechanism of condensate gas in Bozhong19-6 structure. In the natural gas fluid containing crude oil, the early crude oil dissolves in the later charging natural gas with the increase of underground temperature and pressure, thus forming the present condensate gas reservoir.