Abstract: The parallel multi-pulse solid rocket motor is more flexible in energy distribution management than the serial multi-pulse solid rocket motor. In order to realize the opening performance of pulse separation device in a parallel multi-pulse solid rocket motor, a ring-distributed metal diaphragm partition structure for parallel three-pulse solid rocket motor was designed. The stage II and III opening process of the metal diaphragm was numerically simulated. The influence of the effective thickness of the diaphragm and the bottom angle of the U-groove on the opening pressure of the diaphragm was analyzed by explicit dynamic simulation, and the thermal combustion opening test of the metal diaphragm was designed for verification. The results show that the metal diaphragm cracks propagate along the U-shaped groove and eventually fracture into several fragments. The opening pressure of metal diaphragm is positively correlated with the effective thickness of the diaphragm, and the opening pressure increases with the increase of the effective thickness of the diaphragm, and the effect is significant. There is a nonlinear relationship between the opening pressure of the metal diaphragm and the bottom angle of the U-shaped groove. With the increase of the bottom angle of the U-shaped groove, the opening pressure first increases and then decreases, reaching a maximum at approximately 65°. By monitoring the pressure on both sides of the thermal combustion open test metal diaphragm, the experimental value of the opening pressure is 1.30 MPa, which is 6.2% different from the simulation calculation result of 1.38 MPa, verifying the reliability of the numerical simulation.