[Objective] The relationship between water content, dry density, shear strength and erosion modulus of laterite in Yunnan Privince, was studied under rainfall condition, in order to provide a theoretical basis for further studies on the erosion mechanism of laterite. [Methods] The methods included artificial simulated rainfall and soil trough model experiments, soil test and relative theoretical analysis. [Results] (1) The relation of the cohesion of laterite with water content showed a quadratic curve relation. Near the optimum water content, the maximum cohesion occurred. The internal friction angle was approximate to the linear relationship with the water content change, and the internal friction angle decreased with increasing water content. Under the conditions of initial dry density 1.0, 1.1, 1.2, 1.3, 1.4 g/cm³, the correlation coefficient(R²) between cohesion and water content ranged from a minimum of 0.754 to a maximum of 0.934, and the R² between internal friction angle and water content ranges from the minimum of 0.944 to the maximum of 0.996. (2) The relation between cohesion and internal friction angle were close to linear relationship with the change of dry density. When the water content was constant, the curve of the relationship between cohesion and internal friction angle with the change of dry density had a certain variation, and the cohesion and internal friction angle increase with the increasing of dry density. (3) The shear strength decreased with increasing water content, and the amplitude was especially obvious when the water content was higher than the optimum water content. The shear strength increased with increasing dry density. (4) By the end of the rain, for laterite with different dry densities, the relationship between the slope erosion modulus and the shear strength showed a quadratic curve relation, and the correlation coefficient (R²) can be up to 0.988. [Conclusion] There is good correlation between the shear strength and the slope erosion modulus, and estimating the amount of the slope erosion with the shear strength of laterite after rain is possible.