Abstract: With the gradually intelligent, large-scale and unmanned coal mine equipment, the requirements for fault diagnosis technology of emulsion pump are becoming higher and higher. The leakage fault of emulsion pump affects the operation sensitivity and accuracy of hydraulic support. In order to diagnose it in time, a method of identifying the leakage fault of outlet valve based on the outlet pressure pulsation signal is proposed. The pressure pulsation mechanism and signal distortion of leakage valve of emulsion pump are studied from three angles: mathematical theory, model simulation and test signal. Taking BRW125/31.5C emulsion pump as an example, the mathematical model of flow distribution in a working cycle after the leakage of the outlet valve is established. Based on the fourth-order Runge-Kutta algorithm, the numerical solution of the mathematical model is obtained by MATLAB, and the pressure of the single volume chamber under different working conditions is simulated. Based on AMESim simulation software, the pulsation law of the outlet pressure of the whole pump is studied, and the influence of the leakage of the outlet valve in different degrees and different positions on the outlet pressure curve of the whole pump is analyzed. Different gaps were set on the spool of the outlet valve to simulate the severity of leakage. The comparison tests were carried out under normal, slight, moderate and severe leakage conditions respectively, and the correctness of the simulation model was verified. The results show that in the mathematical model, with the increase of the gap between the valve core and the valve seat, the corresponding volume cavity and atmospheric pressure difference of the faulty valve decreases during the suction stage. In the physical simulation model, the leakage degree of the outlet valve is inversely proportional to the pressure difference between the volume chamber and the atmosphere in the suction stage and the outlet pressure of the whole pump. The outlet pressure of the whole pump presents the law of continuous alternating pressure supply of single volume chamber and double volume chamber, and the leakage of outlet valve A mainly affects the first three parts of a cycle of the outlet pressure curve of the whole pump. The leakage of the outlet valve B mainly affects the first, fifth and sixth sections of a cycle; Outlet valve C leakage mainly affects the third, fourth and fifth sections of a cycle. The law obtained by the actual test is consistent with the simulation law, which proves the feasibility of fault identification of the outlet valve through the distortion of the outlet pressure curve.