The strength of rockmass f rom two aspects is analyzed. Firstly, the strength of the rockmass is mainly controlled by the critical stress value of rock, and the contribution of joints is to increase the effective stresses of rock and to decrease the damage strength of rockmass according to the macro2damage mechanics of rockmass. Secondly, the strength of rockmass is mainly controlled by the f racture strength of joints. Based on the comprehen-sive analysis and comparison for the damage strength of rockmass and the f racture strength of joints, a composite damage theory of rockmass may be established.