Abstract: Aiming at the sensitivity of modified red clay to many strength factors, the unconsolidated and undrained triaxial test of red clay with various gradients of nano-graphite powder under different moisture contents was designed, combining SPSS multiple regression analysis and MATLAB data fitting, which obtain the mathematical model between intensity and various factors. Analyzing the effect of nano-graphite content on the microstructure of regional red clay with SEM method. The results show that:The appropriate amount of nano-graphite powder has a significant effect on improving the mechanical strength of red clay, and its addition ratio is the most sensitive factor affecting the strength of regional red clay. The mathematical model established by the fitting curve of shear strength and cohesive force with the addition ratio shows that the shear strength and cohesive force c increase first and then decrease with the increase of nano graphite powder,while the internal friction angle is basically the same. The content of nano-graphite changed the microstructure of red clay to varying degrees, resulting in a gradual transition from a loose state to a dense state on the surface of the soil surface particles, which ultimately changed the strength properties of red clay.