High performance parallel computing platforms are built by interconnecting a group of PCs. The parallelized 3D FDTD code is achieved and is useful for the studies of the transmission properties of photonic crystal slab W3 waveguide. The analysis of the performance of parallel environment indicates that for a large-scale computation problem,the parallel FDTD algorithm can achieve a better fixed speedup. Transmission spectrum and field distribution of a photonic crystal slab W3 waveguide are calculated with the use of the presented technique,and the obtained results show that photonic crystal slab W3 waveguide can control the propagation of light in the three directions and there is mini-gap for the guides.