Abstract: This work studies the probability of clobber(P_c) of a cruise missile's low height terrain following flight. It deduces the computation method of the clobber probability, puts forward a set of practical formulas for computing the probability of clobber, while taking the influences of both the random input of terrain and the random interference of wind at low height, and the characteristically long-time very low height terrain following flight of missile into consideration. Using them and taking the parameters a₂₄ and K_h as an example, under given condition, the correlative curve of the parameters and the probability of clobber is worked out, the parameters' influence on the probability of clobber is analysed. The conclusion is that, to co-ordinate the parameters such as a₂₄ and K_h can reduce the clobber probability effectively, and at the same time enhance the warring capability of the cruise missiles.