Abstract: In the process of using PVTsim to simulate the formation of the paleo-pressure, the clear relation between the simulation results of volume ratio of gas to liquid and the trapping pressure was found, the functional relation between the ratio of gas to liquid and the trapping pressure was given, then the ratio of gas to liquid measured under the room temperature in laboratory was added into the formula and finally the simplified method of hydrocarbon-containing saline inclusion was obtained, which is convenient to simulate the pressure of mass inclusion samples and provide a reference for the correcting of the components of inclusions and the simulation results. The method was applied to simulate the evolution process of fluid pressure in Paleozoic strata of well Lin-1 in southeast Sichuan, the results showed that the overpressure of well Lin-1 generally existed during early Paleozoic, the pressure coefficient of the early Cretaceous was more than 2.0. In late Cretaceous, the formation depression declined rapidly, and it is normal in present stratum, which shows that the late strong tectonic uplift had a significant damage to the overpressure of the stratum.