Abstract: Aiming at the problem of low seismic intensity while drilling, which is detrimental to the anti-collision monitoring between boreholes, an energy storage downhole seismic generator was designed.This generator is composed primarily of a piston, spring, impact hammer, anvil and a delay device. It was able to achieve high efficiency impact by means of the energy storage of drilling fluid. In order to achieve the optimal performance, taking the impact hammer as research object, the impact hammer flow passage model of downhole seismic generator was established. With the CFD software, the influence law on the output performance parameters of downhole seismic generator brought by the spring stiffness, impact hammer mass, throttling area, the outlet diameter, quantity and drilling fluid density were analyzed based on the CFD dynamic grid technology. The results showed that the throttling area, number of outlets, outlet diameter and drilling fluid density were positively correlated with the output performance parameters of downhole seismic generator. The greater the spring stiffness, the smaller the displacement corresponding to the maximum impact energy of the impact hammer. Correspondingly, the greater the mass of the impact hammer, the lower the velocity. Based on the results of single factor analysis, and by taking the impact energy of impact hammer as the optimization target, the optimal combination of design parameters was obtained by the orthogonal test. The results indicated that each design parameter had its unique effect on the output performance of downhole seismic generator. While the outlet diameter and spring stiffness play a prominent role on the output performance of the generator, the throttling area, hammer mass and number of outlets have a significant role on it, and the influence of drilling fluid density is not significant.Thus, the optimal combination of design parameters was selected based on the research results, which can provide a basis for the design of downhole seismic generator.