Abstract: Outer collapse coordination system is a rock mechanics calculation system with outer collapse angle and main stress as its dependent variable, while Moore limit stress circle is with internal friction angle of rock and main stress as ins dependent variable. The relationship between the basic mechanics parameters of the two systems is corresponding conversion. Outer collapse coordination system can describe the authentic unity of nature collapse of rock, rock test and rock mechanics. Moore limit stress circle can describe the basic mechanics characteristics of rock during the rock test. The stress described by geometrical graph is different from normal definition. There is limitation of basic expression. The relationship has not been built up between stress of rock test and stress of surrounding rock mass.

Key words: outer collapse angle coordination system, Moore limit stress circle, stress relationships, comparison