Abstract: According to the phenomenon of attenuation of mechanical parameters in rock failure, the strength criterion for intermittence jointed rock mass is proposed by use of the attenuation formula of virtual joint mechanical parameters based on the Jennings Criterion. The strength criterion for intermittent jointed rock mass and the attenuation formula are applied into the DDA code to complete the computation program of analyzing the initiation, extending and connecting of rock fractures, and then the validity of algorithm is verified by making comparison between the computed results and the shear test ones. At last, this algorithm is employed to analyze the stability of surrounding rock of Jingjishan Tunnel, which is a multiple-arch tunnel with eight traffic lanes. The simulated results show the influences of joint distribution features on the surrounding deformation and give the characters of surrounding displacement. It is shown that the fracturing algorithm of intermittent jointed rock mass is capable of analyzing the stability of tunnels.