Abstract: According to the data of XRD and SEM, the authors studied the content, morphological characteristics of clay minerals in the tight sandstone reservoir, analyzed the evolution process in different diagenetic stages and their influence onthe physical property of sandstone reservoirs in Huagang Formation. The study shows that kaolinite and montmorillonite had important effect on potassium feldspar resolution in the diagenesis. Enough kaolinite and montmorillonite promoted the resolution of feldspar and the development of secondary pore. Otherwise, less feldspar resolution means less secondary pore. With the intensification of diagenetic degree, the content of chlorite and illite increased. Correspondingly, the porosity of reservoir didn't alter obviously, but the permeability decreased dramatically. It is thought that with the increase of chlorite clusters and illite fibers they blocked the fine throat and deteriorated the permeability.