Abstract: Lots of cutting slopes were developed in building along the highway from Yichang to Badong, where the ground was covered by the residual unsaturated red clay. The soil strength fell sharply under rainfall, which caused a large number of cutting slopes to lose stability. Currently there was little experimental study in strength and deformation characteristics of Badong unsaturated red clay. To investigate the effect of matrix suction to the shear strength of red clay, the soil-water characteristic curve and triaxial strength test of the red soil were conducted. The triaxial shear test was conducted by using GDS triaxial system with double pressure chamber. The results show that the matrix suction has a major influence on soil strength. When the matrix suction is controlled, the soil strength has a nonlinear growth with the matrix suction increasing; the matrix suction gets lower as the soil water content increases. That's to say, the strength characteristics of Badong unsaturated red clay can get worse with soil water content increasing. Finally, the shear strength formula of Badong unsaturated red clay was fitted. The research results can be used for engineering practice in this region.