In FRC experimental studies, it is found that the parameters of the plasma formed after the collision merging greatly depend on the plasma parameters of the formation zone. The design and optimization of the pulsed gas injection device will help the ionization of neutral gas and thereby improving the plasma parameters of the formation zone. In this paper, studies are focused mainly on the change process of gas distribution of pulse gas injection stage, and design of the pulse gas injection device. The research takes the control of gas distribution as the goal and ANSYS FLUENT as a simulation platform to carry out the study. First, in this paper, we introduce several gas injection schemes that can be used in the pulse gas injection device, and ANSYS Fluent is used for simulation comparison. Through the analysis of simulation results, we have determined the most suitable scheme for gas injection. Then, we analyze in detail the axial and radial distribution of neutral gas at different time under the optimal scheme. And the results show the advantages of multi-valve gas injection. Finally, we predict the appropriate time duration of gas injection and ionization time when the pressure source is 2 × 10^5 Pa.