Abstract: When crawler tractors travel on sloped terrain, the maximum shear stress of soil exerted by tracks serves as basis for powering tractor．The classical Coulomb formula does not take into account practical factors such as soil moisture content, track shear rate, and slope angle, and it cannot be directly applied to mechanical performance analysis of crawler tractors under slope conditions．In response to this issue, direct shear tests were conducted under different soil moisture conditions to obtain a mathematical model of variation of soil shear strength parameters with moisture content．Influence of track shoes on the maximum shear stress of soil under different shear rates and slope angles was investigated using a quadratic orthogonal combination experiment, and the classical Coulomb formula was modified．Verification test showed that under different soil moisture content, shear rate, and slope angle conditions, relative error between the maximum shear stress test value and theoretical value was less than 5%．This indicated that modified Coulomb formula could accurately reflect influence of various factors on the maximum shear stress, and could provide a theoretical basis for driving mechanics calculation and performance analysis of track tractors under slope road conditions．