In order to study the water-sensitive properties of Bijie red clay, the basic physical index test and direct shear test of different water content samples were carried out. The relation between shear strength index and water content of red clay was obtained, and the influence of critical water content on strength was analyzed. The testing results show that the shear strength index of Bijie red clay turns around the natural moisture content, because of the cracks generated with water losing. Then the functional relationship between cohesive force, internal friction angle and water content was established. Based on this relationship, it can reflect the quantitative influence of water content on intensity.