Abstract: Electromagnetic PIC simulation contains three key computational procedures: solving Maxwell’s equations, solving Lorentz equation and particle motion equation, updating charge density and current density. According to the characteristics of the three computational procedures, parallel algorithms based on OpenMP were designed. Then the performance of the parallel algorithms were tested and analyzed. In the light of the performance analysis, the parallel computation based on OpenMP of CHIPIC3D software was implemented. At last, the parallel version of CHIPIC3D was used to simulate a kind of extended interaction oscillator, and the results show the parallel algorithm is correct and the speedup is enhanced.