Abstract: The physical and mechanical properties of expansive soils were discussed in this paper. Relevant geotechnical experimentswere performed and the principal internal factors and external conditions, which determine the expansibility and contractibility of expansive soils, were obtained. In order to improve the self physical and mechanical properties of expansive soils, several disposal programs, in the two facets of ground treatment and engineering construction respectively, were adopted to solve the hazard to the highway resulted from the expansibility and contractibility of expansive soils roadbed. According to the application in the engineering, it is proved that these measurements were effective.