Surface Plasmons(SPs) can process visible light and infrared light in subwavelength scale, which can provide a huge boost to the development of optical integration. The theoretical basis of the Finite Difference Time Domain(FDTD) method is introduced, and a slow-light waveguide with Metal- Insulator-Metal(MIM) structure is designed. An analysis on dispersion property, group velocity and field intensity distribution of this waveguide is performed with FDTD. It is shown that the waveguide can support slow light propagation and suppress the pulse distortion into some tolerable values simultaneously, when setting the frequency in an appropriate region in the dispersion curve.