In order to understand the objective distribution regularities of hydrocarbon near the faults in a petroliferous basin.Methods:The determining method of the hydrocarbon leakage period has been constructed based on the mechanisms and time units of leakage in fault—caprock configuration, which was established by determining the time when a fault starts to destroy the sealing of mudstone cap and seal hydrocarbon by forming some fault rocks and ceasing activity. Then by analyzing the F3 in the Oilfield- 5 in the Nanpu Depression, Bohai Bay Basin, this method was applied to the determination of oil—gas leakage period of mudstone caprock configuration (Ed2). Results: The results show that the destructive effect to the mudstone cap of Ed2 is limited by F3 of the Oilfield- 5 in the Nanpu Depression, only the fault—caprock configuration fails and oil—gas leakage occurs at the Point P2 and P8. The oil and gas leakage periods of P2 and P8 are about 16~7.4 Ma and 13.6~4.8 Ma respectively. Conclusions: There is few difference with the oil—gas leakage period of the fault—caprock configuration between P8 and P2. However, the oil—gas leakage period by fracturing at P8 was obviously shorter than P2, which is favorable for hydrocarbon accumulation under the mudstone caprock of Ed2 at P8. This analyzing is consistent with the current situation of petroleum exploration near F3, the situation shows that hydrocarbon was founded at P8 instead of P2 under the mudstone cap of Ed2, which means that this method is feasible for determining the period of oil and gas leakage.