Abstract: The failure process in geo-engineering, such as slope, tunnel and mine, is always accompanied by rock dilatancy. So the studies on the rock dilantancy can really make sense for evaluating the stability of rock mass. TAW-2000 servo-controlled triaxial rock testing system is employed to reveal the rock dilatancy behaviors through uniaxial or triaxial tests on 8 different kinds of rocks. The following conclusions are drawn through the analysis of the test results. The stress of rock dilatancy onset increases with the confining pressure. Compared with that of the peak stress, the variation of stress increment of the rock dilatancy onset is greater. The formula for the stress ratio-axial strain ratio is defined. The relationship between the stress ratio and the axial strain ratio is linear through the origin point regardless of the lithology and the confining pressure. If the stress-strain relationship of the peak is known, the rock dilatancy onset can be found easily. More and more importance should be attached to the studies on the rock dilatancy onset and the peak, that is the key issue for long-term stability estimation of the rock mass.