Abstract: Faults are well developed in the Subei Basin.The formation of oil reservoir is closely related to multi-control actions of fault passage and fault sealing.Oil reservoirs are mainly complex fault block reservoirs.Based on the analysis of oil reservoir and characteristic of fault seal data set,4 types of essential sealing modes are developed in this paper,which include butt joint seal mode of sand and mud layer(type A),mixed seal mode of sandstone and mudstone of layers(type B),time match sealing mode(type C),and principal stress sealing mode(type D).Type B,C,and D are further classified by forming mechanism and controlling factors of sealing.According to the above,4 parameters controlling fault seal and quantitative evaluation system of fault seal are set up,which are widely used in petroleum exploration and exploitation with immediate effect and economic benefit.