Abstract: From the view of the mass intensity theory，the stability evaluation method of rock mass under the initial ground stress field is analyzed quantitatively，and the correlation between the initial stability of rock mass and the occurrence of underground dynamic disaster.Based on the Mohr-coulomb strength theory，the Mohr-coulomb stress （W_σ）evaluation index are derived to reflect the level of rock approaching to the limit damage intensity under a stress state before damage.W_σ can represent rock stress is close to the failure limit under uniaxial compression，uniaxial tension，three directional stress，and compression-tension.The closer W_σ is approaching to 1，the closer the rock is to the failure limit，meanwhile，the worse stability the rock has.The description of initial ground stress field of rock mass by W_σ can express the proximity extent of the rock mass stress state and the limit state，which is helpful to determine the rock mass stability under initial stress field.Where the rock mass has the worse initial stability owns a higher probability in occurrence of dynamic disaster of rock burst.According to the W_σ，5 stable zones such as high stable，higher stable，med-high stable，lower stable，low stable level are divided to evaluate the initial stability of rock mass.The research can provide references for predicting the impact ground pressure and other geological dynamic effect induced by the engineering activities.

Key words: Initial ground stress field, Stress state, Dynamic disaster, Danger zone