Abstract: Based on the deformation and failure phenomena of the projectile penetration into rock,the zone near the cavity of penetration is divided into failure,elasticity and crack zone.Considering the influence of friction coefficient of sliding,the resistance of warheads is gotten by use of the dynamic equation of intrinsic friction medium near the cavity of penetration.The relation of scale conversion is gotten by use of the mass conservation equation.The expression of depth of penetration is gotten by means of the motion equation of projectiles according to the Newton’s law of motion.Considering the examination data from empirical formulas,the expression of friction coefficient of sliding is gotten.Through the calculation,the choice of coefficient has rather great influence on the depth of projectile penetration.Then the influence of the change of projectiles on the coefficient is analyzed.By comparing the calculated results with experimental formulas,the sliding friction calculation formulas have highly accurate and practical characters and will provide the strong reference for the design of warheads.