Abstract: Microseismic monitoring technology has been widely used in rock mass engineering monitoring. There are still many problems in stability evaluation of rock mass engineering using the microseismic data. In this study, microseismic energy density is proposed to characterize the micro-crack distributions of rock mass based on the quantitative seismology. Besides, the energy-frequency relation is derived theoretically and the b_εvalue is used to represent the micro-cracking deformation. Then the microseismic energy transference and evolutions of focal mechanism, micro-cracking deformation and stability of Dagangshan right bank slope before and after reinforcement by anti-shear tunnels are discussed. Some conclusions are drawn as follows: Firstly, potential dangerous area of the slope can be determined using the microseismic energy density, and evolutions of micro-cracking deformation and rock stability are revealed by tracking the variation of b_εvalue in the energy-frequency relation. Secondly, the microseismic event rate and energy density decrease significantly after reinforcement, and its mechanical behavior is obviously improved. Finally, the b_ε value of reinforced rock masses decreases slightly along with slope excavation and increases after reinforcement, which demonstrates that the micro-cracking deformation is controlled and the stability is improved after reinforcement, and these are in accordance with the monitoring results of slope deformation, validating the reliability of the proposed method, which enriches the microseismic analysis methods for rock mass engineering stability. It may provide references for choosing