The dam of Qiaoqi Hydropower Project is 123m high, in which it is the first time for the spreading gradation crushed stone-earth to be adopted as the impervious material for so high an earth — rock dam in China. Study about the engineering application is conducted. First, a lot of experiments about the engineering characteristics are done indoors to analyze the feasibility fo this kind of material in whole material storage, based on which, the control standards of design and construction are recommended. Second, the representative earth sample is selected to verify if the control standard is reasonable by rolling experiments on site. Finally, the three -dimension stress and strain and seepage about the dam body and foundation are calculated to analyze the rationality of the control standard for these materials and the safety factor of the dam under all the actions together. This article states the methods, process and results of the study on the impervious materials and proposes the design and construction control standards for the impervious material used as the core wall.