Abstract:A cylindrical cavity expansion model for rock targets with penetration of long rod projectile is presented by using the unified strength theory which consists of a generic of convex piecewise linear yield criteria. The relationship of cavity expansion pressure and cavity expansion velocity is obtained. The analytical equation of penetration depth is given and the penetration depth of long rod projectiles when impacting rock targets at 450 ~ 1 400 m/s is calculated. The results are compared with experimental data. The influences of the weighting coefficient b of the unified strength theory on the penetration depth are investigated.