Abstract: Based on the modified Drucker’s postulate and the internal variables theory of constitutive relations，the general incremental constitutive relations for the general viscoplastic yield models of damaged materials are deduced, and the pertinent strict incremental constitutive algorithm for Mohr-Coulomb model with strain-rate effect, which is often used in rock and soil mechanics, are obtained. The presented strict incremental algorithm is an explicit form with the incremental stress calculated by increment strain, which is particularly convenient and applicable to high velocity impact problems. As an example, the computational simulation for the problem of spallation caused by the impact of two rock slabs is carried out. Based on the presented increment constitutive algorithm, the results are satisfactory.