Considering the effect of magnetic field on the plasma plume, a hybrid particle-fluid model combining DSMC and PIC methods was developed to study the plume characteristics of a pulsed plasma thruster. By incorporating a magnetohydrodynamic code to provide inlet conditions, this model was applied to simulate the three-dimensional plume field. The calculation results were validated by an experiment based on triple Langmuir probes. Investigations show that there are substantial differences between the expansion dynamics of various species. It is indicated that the oscillation of discharge current will lead to the generation of a population of low-velocity ions, together with the aggravation of backflow of ions. Electromagnetic acceleration is demonstrated to be the primary mechanism of plasma acceleration, and the magnetic field plays an important role in the diffusion of the thruster plume.