The study of the parametric theory of bidirectional reflectance distribution function (BRDF) for the coating material is presented. The 3 parameter formula of BRDF is obtained. By optimizing the parameters, the parametric models of BRDF for several typical coating samples are demonstrated. A comparison of this parametric model with the experimental results shows that both results are in agreement well. This method for calculating BRDF of rough surface is simple in form and practicable in the engineering applications.