Abstract: The material characteristics of the overburden layer is an important factor for the success of the natural caving method. The overburden of the natural caving mining method in Plan copper mine is a granular body of plateau moraine, whose shear strength parameters are closely related to moisture content. Based on the direct shear test method, the shear strength parameters of moraine at high altitude were obtained under different water content conditions, the relationship between moisture content and shear strength parameters of moraine debris was also discussed. The results were as follows: the cohesion and internal friction angle of plateau moraine particles decreased with the increase of moisture content. There was a strong logarithmic relationship between cohesion and moisture content, and an exponential relationship between internal friction angle and moisture content. Based on the law of variation between shear strength parameters and water content of moraine, cohesion was more sensitive to the change of water content, while internal friction angle was less sensitive to the change of water content. The results showed that the sensitivity of cohesion to water content was stronger than that of internal friction angle. The effect of moisture content on the shear strength of moraine debris was mainly reflected by the change of cohesion. The research results in this paper can provide some theoretical basis for the study of glacial till cover layers in high−altitude areas.