Abstract: The conservation and reinforcement of earthen sites is extremely urgent. especially in northwest of china, because of the special geography and climate environment, soil sites are destroyed obviously. To prolong their life and make them exist for longer time, many effective materials have been invented during the period of conservation and reinforcement of earthen sites. In this article we researched on PS material and chose the soil of Jiaohe and Gaochang ancient cities. The reinforced raw and remoulded soil with PS has been tested their intensity, anti-drenching ability and anti-aeolian erosion ability etc. The intensity and durability of ancient city soil reinforced have been studied. A lot of experiments indoor indicate: after reinforced by PS material, the intensity, anti-drenching ability and anti-aeolian erosion ability of the soil have been improved obviously. It shows that PS material has clearly results of reinforcement, and it will offer valuable theory and direction for further use of PS material in conservation and reinforcement of soil site.