Abstract：The empirical methods are used to evaluate various projectiles damage to rock medium in the design criteria of protective engineering of most countries，but they are not considered in the current standards in China. The function relations of the crater scaling-radius with projectile penetrating-depths and projectile charge parameters are established according to the similarity theory. An empirical formula for evaluating the craters，which is created by the explosion of the BLU–109B earth penetrating model projectile in the rock，is presented by the experiments and the statistical regression analysis，and the curves expressing the effect of velocity and charge of the projectile on the radius，deep and volume of the craters are obtained under the condition of the same rock. The analysis of the experimental results shows that the size of crater radius depends mainly on the velocity of projectile，the charge and the mechanical properties of rock. The velocity of projectile is a major factor for damaging rock under the condition of the same charge and the same target. When the velocity of projectile is lower than 450 m/s，the crater radius depends mainly on the crater radius created by the projectile penetration，and when the velocity of projectile is higher than 450 m/s，the crater radius depends mainly on the crater radius created by the charge explosion，and the crater volume quickly increases with the velocity of projectile.
