In order to study the mechanical properties and failure mechanism of unloading damaged surrounding rock, RMT-150 rock mechanics test system was selected to carry out tests on triaxial rock in loading-unloading process to prepare damaged rock. Combined with AEwin acoustic emission system, the uniaxial reloading test was conducted on damaged limestone, the relationship curve of stress-time-energy accumulation was tested, and the macroscopic failure characteristics of the rock were analyzed. Experimental results show that with the increase of unloading points, the damage degree and failure form of the damaged limestone were changed obviously. The failure form of the limestone transformed from brittle failure to ductile failure, and the phenomenon of expansion was less and less obvious. In the process of uniaxial loading, the variation in the cumulative value of the acoustic emission energy of the damaged rock with peak strength lower than 70% tended to be the same, which can be divided into three stages: stable stage, stable growth stage, and secondary stable stage. The distribution mode of micro-cracks in rock had an obvious influence on its macro-failure characteristics, and the micro-mechanical response of rock determined its macro-mechanical failure characteristics.