Abstract: Nowadays, Finite Difference Time Domain (FDTD) has been applied widely in electromagnetic calculations.But when it is applied for complex electromagnetic problems, the FDTD method may cost a lot of computation time and hugecomputer memory, which has already become an urgent problem needed to be solved. This paper introduces a strategy forparallel implementation of FDTD algorithm based on MPI parallel environment. The efficiency of parallel FDTD using different MPI communication methods is measured. On a Beowulf PC cluster system with 16 nodes, an optimizedthree-dimensional FDTD parallel program using the Put operation and the General Active Target Synchronization (PSCW)achieved a highest speedup ratio and parallel efficiency.