Abstract: In this article, the parallel performance test of JEMS- FDTD on MPP(Massively Parallel Processor) is introduced, including the performance of different patch size, single- node and multi- node MPI/OPENMP hybrid parallel performance, and large scale parallel performance. The test shows that JEMS- FDTD is capable of performing parallel computation on tens of thousands processor cores efficiently. The computation and analyzing of a computer case with complex structure illuminated by pulsed electromagnetic wave is introduced an example, which demonstrates JEMS- FDTD’s capability of solving electric- large- scale electromagnetic propagation, radiation, coupling problems on MPP with high efficiency.