Abstract: Based on the study of factors influencing the sealing of oil/gas, this paper pointed out thickness, abnormal pore fluid pressure and the sealing of faults to be the main factors controlling the sealing of caprock for oil/gas. The continuity of original space distribution of the caprock with big thickness is good. Even if the caprock with big thickness were destroyed, distribution continuity would not easily lost. The caprock with big thickness owns strong capillary sealing ability, can form abnormal pore fluid pressure and the restraining hydrocarbon concentration sealing. Abnormal pore fluid pressure can enhance capillary sealing ability of caprock and the restraining hydrocarbon concentration sealing ability making faults form sealing. The sealing of faults can recover the quality and the continuity of space distribution of caprock.