Abstract: We present the experimental results on the laser back scattering characteristics,such as laser radar cross section,of very rough surface of steel and coated surface at λ=633nm and λ=904nm with a laser scattering automatic measurement system.Based on scattering theory of rough surface,we built up the double ruler model of the rough surface,and utilize phase method and scalar approximate method of Killhoff theory to theoretically calculate the angle distribution of laser back scattering intensity for a specimen of rough surface,at λ=904nm.The experimental results are well agreement with theoretical calculation.