Abstract: By taking the plume of a pulsed plasma thruster (PPT) as research object,a three-dimensional physical model in a Cartesian coordinate system was developed,and the electron momentum equation was simplified and discreted to simulate the unsteady flow of plume employing particle-in-cell (PIC) and direct simulation Monte-Carlo (DSMC) hybrid method. Assuming that the propellant particles were injected to the flow field by a sinusoidal rule during a pulse period,the time-dependent profiles of potential,electron,ion and neutral number density were analyzed. Then the simulation model was verified by making comparisons between computational results and experimental data. The research indicates that the model could predict the parameters of the plasma plume in both parallel and perpendicular planes to electrodes. And the research method and findings can provide a reference for further study on PPT plume.