Abstract: Based on field investigation and direct shear test calibration,PFC^2D numerical simulation was used to analyze the relationship between shear strength and temperature,rock debris content,gravel content,and particle size of polycrystalline ice,ice-rock mixture,rock debris ice,and gravel ice. Experimental verification was carried out. The results show that:(1)The shear failure of crystalline ice occurs along the maximum shear stress surface,and the shear failure of ice-rock mixture occurs along the contact surface of ice-rock. Their fracture surfaces are flat. The shear failure characteristics of rock debris ice and gravel ice are related to particle content and particle size,and the fracture surface is uneven. (2)The shear strength of glacier ice decreases with the increase of temperature. It decreases linearly at -40℃ to -10℃,while the influence is more significant below -40℃ and above -10℃. The internal friction angle is more sensitive to temperature than cohesion. (3)The shear strength increases with the increase of rock debris or gravel content. When the content increases from 0 to 20%,it has a greater influence on the internal friction angle and a smaller influence on the cohesion. When the content increases from 60% to 80%,the effect on cohesion is more significant than that on the internal friction angle. When the content is 20% to 60%,both of them increase linearly. (4)With the increase of gravel particle size,the internal friction angle increases first and then decreases,while the cohesion decreases first and then increases. When the gravel particle size is about 12.5mm,it reaches the maximum and minimum values,respectively. The research results have scientific value and practical significance for revealing the mechanism of ice avalanche and disaster prevention.