High in-situ stress is one of the main properties of deep rock mass.As the depth of mining，tunnel excavation，etc. increases continuously，the high in-situ stress in deep rock mass represses the effect of water-coupling blasting.Therefore，how to apply the method of water-coupling blasting in breaking deep rock mass with an aim of whether inducing considerable fracture and fragmentation of rock or obtaining the optimal economic benefit has become an essential problem in the field of blasting engineering.In order to study the mechanism of crack propagation under water-coupling blasting in deep rock mass with high in-situ stress，based on the RHT material model verified by experimental results，a series of numerical models were built and the multi-core dynamic analysis finite element software LS-DYNA was applied to simulate the crack propagation of a single hole with a water-coupling charge under different in-situ stress conditions.Numerical models were built under condition that decoupling coefficients were set to 1.11 to 10，with in-situ stress of 0，10，20，30，40 and 50 MPa.The process of crack propagation under water-coupling blasting with high in-situ stress was first analyzed，and then the influence of in-situ stress on the water-coupled blasting was investigated.A comparison of the results of rock blasting with air and water was conducted.And the rock crack evolution with different water-coupled coefficients and different ground stresses was studied.According to the simulation，the water-coupling blasting under high in-situ stress generates three damage zones，i.e. the crushed zone，the nonlinear fracture zone and the radial crack propagation zone.The water-coupling method prolongs the time of explosion and increases the peak radial stress and PPV in rock mass，and it makes the effect of rock blasting better.In-situ stress plays a role in increasing stress and PPV of rock mass under water-coupled blasting in deep rock mass，and high in-situ stress significant inhibits the rock crack propagation in radial crack propagation zone but has no much influence in crushing zone and nonlinear fracture zone.With the decrease of water-decoupling coefficient，the extent of rock fracture increases rapidly.The optimal water-decoupling coefficient exists under different in-situ stresses，by considering the utilization of explosive energy，and the optimal decoupling coefficient decreases with the increase of in-situ stress.The optimal water-decoupling coefficients at in-situ stresses of 0，10，20，30 and 40 MPa are 5.00，3.30，2.63，1.56 and 1.25，respectively.This study provides not only an analysis of the rock crack evolution under the combination of water-coupled blasting and high in-situ stress but also a reference for resolving excavation difficulties in deep rock mass.