Abstract: The mositure content is an important controlling factor of the mechanical property of unsaturated soil.The main kind of soil mass surrounding Beijing Suzhoujie Subway tunnel is unsaturated cohesive soil.By using the method of drill sampling the samples of the soil mass system around the tunnel area were obtained.The relationship between the deformation and strength and the moisture content of the unsaturated cohesive soil mass were established through triaxial tests.And furthermore the relationship between the main parameters and the moisture content of the unsaturated cohesive soil mass were established. Based on that,the mechanical parameters of the soils in different areas of the construction site were determined.Through the analytical method of finite element numerical modeling,the stability of the soil mass and the ground settlement during the construction were studied.And the stability of the soil mass during the construction of tunnel with the consideration of the moisture content variation were made clear.