The mechanical properties of unsaturated soil under different normal stresses and water contents were systematically studied with the cyclic simple shear test, where the water content is 5.4%～25.4% and the normal stress ranges from 25 kPa to 300 kPa. It mainly investigated the influence of the normal stress and water content on the mechanical properties of unsaturated sandy soil. Experimental results show that there is an equilibrium water content. When water content is greater than the equilibrium water content, the curve of the shear stress and shear displacement of unsaturated sand soil will change from hyperbolic to Double Broken Line model. The shear stress changes in small range when the water content of the unsaturated sand soil is under the equilibrium point. Whereas the shear stress drops sharply as the water content increases .The water content has important influence on the mechanic performance of unsaturated sandy soil, such as cohesion, internal friction, dilatancy and so on.