A system for the measurement of Terahertz-wave scattering was set up. It includes 0.2THz BWO, pyroelectric detector and an automatic optical table. With this system, THz wave scattered by two copper plates with different surface roughness were measured. The result showed that electromagnetic scattering produced by the terahertz wave induced current and lambert scattering caused by the rough surface of the conductor exist at the same time. The metal rough surface approximated to lambert body could be considered as mirror when terahertz wave was obliquely incident. However, with the increase of roughness, the reflection gets weaker while the scattering becomes stronger, and the main peak shifts toward the angle smaller than that of reflection. Under the situation of normal incidence, the scattering curve decreased more quickly at the scattering angle less than 40?and changed slowly when the angel was more than 40?. For many materials, scattering peak appeared when the scattering angle was around 50?.