To research the regional characteristic and the water-sensitive shear strength of red clay, a series experiments which based on the sample of the red clay located in the Guangdong Yunfu region were done in this article, and the rule of the water-sensitive shear strength was discovered by considering the change of the moisture content directly without measuring the matric suction. The results showed that: The red clay has high moisture content, high liquid limit, high plasticity, contraction dilation, fracture property, high porosity ratio, low compression, and \"pseudo-powder\", etc; Red clay stress-strain curve is the enhanced curve, and there is a large difference between high and low moisture content at shear strength, the shear strength increase with the moisture content decrease. Cohesion with the increase in moisture content, showing a first-order exponential decay, while internal friction angle showing the characteristics of sub-functions; It comes the concept of \"shear strength surface on critical moisture content\" through the water sensitivity test results, and it can be determined that whether the soil reaches the shear strength through a recognition process based on known overlying pressure and wet-dry state of the clay, and this can provide a reference for practical engineering.
