The judgment criterions of the rock mass stability have not arrived at round phase. A series of basic problems have not formed the code for design about the judge rule of the rockmass stability from the definition of stability to the quantitative standard. The range of the stability of surrounding rockmass can be defined by the plastic zone or the displacement changing zone at present. By using the elasticity theory and basic idea of the safety factor in the engineering

the paper develops a new safety factor method based on the element by the Mohr-Coulomb and Drucker-Prager rule. The safety factors are solved by FISH in the FLAC3D. The quantity standard and the safety range of the rockmass stability are developed by the safety factor for the provided reasonable supporting parameter in the reinforced engineering.