Abstract: The results of analysis of more than 7000 clay mineral samples from 20 oil bearing basi ns indicated that the characteristics of distribution and controlling factors are different in conventional,salt alkaline lake,coal bearing and volcanic detritus sedimantary basins.The transformation from smectite to illite and kaolinite to chlorite with depth is obvious in normal basins,and such change of clay minerals is governed domminantly by diagenetic process.High illite and chlorite and low kaolinite is the characteristics in salt alkali basins.This is governed by the condition of the aqueous medium,and typical minerals are obviously different under different condition.In coal bearing basins,the clay minerals are characterized by high kaolin ite content.In volcanic detritus basins,the smectite is widely spreaded and it is mainly governed by the source of parent material and the condition of the aqueous medium.