Abstract: The surrounding rock is often broken rock mass in underground engineering, but it still has certain bearing capacity subjected to rational supporting system. Accordingly, experiments are carried out about the true three axial mechanics experiments subjected to different restraint mechanism. The experiments mainly include the influences about the strength and rigidity to stress and strain after peak strength, and throughout the whole crushing process. Meanwhile, the stress-strain curves are plotted on the same graph, and the constitutive relations are qualitative discussed considering of various factors about economy, security the reliability and efficiency, etc., in the end, the domain of rock constitutive relation is drew. So in the engineering practice, the stress strain values just can fall on the domain before determined. In such cases, it can avoid that constitutive relations is too complicated to convenient generalization problem, and more important, the post peak constitutive relations are consistent to actual engineering rock mass, these make rock mechanics results to transit for rock mass mechanics providing a a new way.