Abstract: As safety valve is an important protection component of hydraulic supports, in order to improve impact resistance of the latter, a two-stage safety valve with a rated pressure of 50 MPa and a flow of 1 000 L/min was proposed, before a mathematical model of the valve was established. Then, coupling effects of structural parameters, such as cross-sectional area of secondary inlet, secondary differential area, stiffness and pre-compression of external spring and others, on the valve's dynamic characteristics were studied through Matlab numerical simulation, and the best matching parameters were obtained. Finally, a dynamic impact test platform was established to test and verify its dynamic features. The results show that when two-stage differential area decreases, and outer spring's stiffness increases, the pressure overshoot, pressure stabilization time and unloading time of the two-stage safety valve are all reduced. The best matching parameters come as 863 mm² for a second-stage differential area and 119 286 N/m for outer spring stiffness, while the pressure and flow stability values are 49.2 MPa and 1 050 L/min, respectively, and the unloading time is 0.02 s. Moreover, simulation and test results are generally consistent.

Key words: hydraulic support, two-stage safety valve, parameter coupling, dynamic characteristics, impact test