Abstract: The Wang zhuang oilfield belong to heavy oil reservoir of strong sensitivity.As a result of the high content of the clay in reservoir,water flooding and pour into steam produce the expansibility results that developed effect isn't ideal.Ther efore,the clay expansibility study is a key technology wich the oil field develop good result.This paper used XRD,IR,DTA.CEC and expansive rate analyses to strees on discussion of the expansibility.