Abstract: With the aggravation of environmental pollution, the urban soils are severely polluted, which makes the research on polluted soils a new topic in the environmental geotechnology and much attention is attracted from the academic and engineering fields. The properties of the foundation soils are changed by acid and alkali pollution. Hence, environmental protection is of great significance for studying the pollution mechanism, survey evaluation and treatment of polluted soils. The polluted soils with 4 different concentrations of acid and alkali are artificially prepared. The strength characteristics of the polluted soils are studied by means of direct shear tests and triaxial tests, and the influences of consistency phase of soils, pore-solid ratio and microstructure on the direct shear strength of the acid polluted soils are analyzed. Based on the relationship between the total stress strength index of acid polluted soils and its concentration, the relevant formula in is obtained, and it is practical in engineering.