The compute of pBRDF model is very complex in most cases. In order to get the contrast of degree of linear polarization(DOLP) between camouflaged target and background accurately and conveniently, the distribution function of microfacet and shadowing function in the Maxwell-Beard BRDF model was simplified with the method of idealization and specific values. The distribution function of microfacet become more accurate than Torrance-Sparrow model and easier than Maxwell-Beard model. According to the property that there are differences between the rate of s component and the p component in Fresnel reflection, the Muller matrix which record the process of reflection was got. Then a polarimetric BRDF model was established by physical theoretical analysis. To cope with in-plane reflection, the pBRDF model was simulated by MATLAB and the results show it can describe the reflecting properties of rough surfaces. The model has theoretical and practical significance for the study of the influencing factors of the reflection by rough surface and polarimetric camouflaged target detecting.