Rock mechanics tests were conducted on typical rockburst specimens to investigate the rockburst features in the diversion tunnel of Jinping second-stage hydropower station. Test results show that the rock samples are complete and hard of high compression strength, with brittle failure as the main failure mode. The rockburst proneness indexes (W_et) of typical strata are larger than 2.0, and rockburst feature is obvious in high geostress area. In the unloading process, the dilatancy of rock specimens is more obvious when the initial unloading confining pressure gets higher. The axial strain of rock specimens when stress falls after peak changes less than that by conventional triaxial tests, and the brittle failure is more obvious when confining pressure gets higher. CT scanning and image reformation results suggest that during the unloading, the rock specimens experience the stage of compaction, state of dilatancy until failure, and then stage of density springback after failure. During the unloading test, failure happens instantly mostly with sounds and double shear damage. Hence the new rockburst criterion and classification standard are proposed using the basic quality indicators of rock mass to describe the hardness and integrity degree of rock. The rock mechanics test results verified the criterion and classification which agree well with the rockburst properties in Jinping second-stage hydropower station.