Based on studying the geological conditions in-fulencing the formation and development of caprocks.this paper divided the development of caprock into two types of the caprock that owns big thickness and continues dis-tribtuion and the caprock that owns small thickness and interbedded uncontinues distribution according to formation environment. Analysis of theory and actual examples incicates that the caprock owns big thickness and continues distribution has stronger capillary sealing ability than the caprock that owns small thickness and interbedded uncontinues distribution. The caprock that owns big thickness and continues distribution has pressure sealing ability. But the caprock that owns small thickness and interbedded uncontinues distribution dosen’t has pressure sealing ability. The caprock that owns big thickness and continues distribution has restraining concentration sealing ability,but the caprock that owns small thickness and interbedded uncontinuous distribution has replacing concentration sealing ability. The caprock that owns big thickness and continuous distribution plays the more important role in formation of oil or gas pools than the caprock that owns small thickness and interbedded uncontinuous distribution.