In order to study the damage characteristics of soft coal under the impact of water jet and the influence of jet parameters on coal breaking performance, the dynamic evolution characteristics of soft coal damage under different jet parameters were analyzed by numerical simulation and experimental research, and the influence of different jet parameters on coal breaking performance was discussed. The results show that under the continuous impact of water jet, the conical, transverse and radial cracks of soft coal gradually develop and extend to the bottom of coal. The number of conical and transverse cracks is better than that of radial cracks. The damage degree increases first and then tends to be stable. After the impact time is 5 s, a stable zone appears. The working pressure of the jet has the most significant influence on the jet shape. The greater the working pressure of the jet, the smaller the reflection angle and the better the coal breaking performance. The working pressure of 10 MPa is the crack initiation pressure of the soft coal body. The angle of the reflected flow gradually tends to be stable when the working pressure is more than 10 MPa. The effective impact damage speed should not be less than 300 m/s, the optimal impact target distance is 5 mm, the optimal nozzle diameter is 1.5 mm, and the optimal incident angle is 75° The research results can provide theoretical support for gas extraction of low permeability soft coal by water jet fracturing.