Abstract: The mechanical parameters of red clay slopes change during the wetting-drying cycles. The failure characteristics and mechanism of the red clay slopes are different from those of the general soil slopes. For the Guizhou red clay, the bath heater-artificial rainfall-simulated wetting-drying cycles are used to prepare a large-scale slope model. The moisture content, pore water pressure and temperature sensors are buried at different positions inside the slope. The evolution law and mechanism of the mechanical parameters of red clay slopes under circulation are analyzed. The results show that with the increase of depth, the soil moisture content of the slope is gradually weakened by the rainfall intensity, and the surface moisture content is obviously affected by the rainfall intensity. The moisture content during the drying period increases first and then decreases. Under the same rainfall intensity, the moisture content at the slope toe is the largest, followed by the slope surface, the slope shoulder, and finally the slope top. The surface pore water pressure increases during rainfall and osmosis, and decreases during drying. The greater the rainfall intensity, the greater the temperature change. As the depth increases, the temperature change of the slope gradually decreases. The temperature at the slope toe changes more than that at other parts. The failure characteristics are as follows: splashing→face erosion→sheet erosion→crack→gulping, and no obvious sliding surface is seen.