The production and practice of coal mines have proved that the dynamical phenomenon in mines have divisional and zoned characteristics. In this paper the division which treats coal, rock and gas as an integrate system by mechanical method is studied. Under study By the analysis of the mechanical property of the coal-rock composite samples and coal simples containing gas under complex stress state, the failure criterion, on the basis of the modification and consummation of the Dracker - Prager´s theory, is set up, and the formulas computing the coefficient of stability and the density of latent elastic strain energy are given. Finally, the fundamental method for deviding the potential danger region (zone) of coal and gas outburst based on the formulas is put forward.