In order to optimize the design of the dam project, improve the construction conditions of filling material of central core, and reduce project cost, we used entirely or strongly weathered sandstone and mudstone as impervious soil in Qingshanzui reservoir ,which is in Chuxiong state of Yunnan province. But the efficiency of seepage control will be affected by excessive mixture ratio of strongly weathered sandstone and mudstone.For the purpose of determining appropriate mixture ratio and finding properties of sandstone and strongly weathered material, we carried out several experiments, in which sandstone and strongly weathered material were mixed under different ratios. Through experiments, results show that, entirely or strongly weathered mixtures of sandstone and mudstone can be used as anti-seepage soil material for central core, and the rational mixture ratio for strongly weathered material is less than 60%, with sandstone less than 25%. Finally, several important technical issues are summarized for the forementioned material.