The polarized reflection light from a target is accompanied by its bi-directional reflection light. To determine the quantitative relation between the polarized reflectance and the bi-directional reflectance on the surface of anthracite, the polarized reflectance on the surface of anthracite is measured at multi-angles and the polarized reflectance and bi-directional reflectance are analyzed according to the degree of polarization. The result shows that the influence of an incident angle on the degree of polarization is determined by the surface roughness and carbon content of anthracite. With the increase of the incident angle, the degree of polarization can be increased in the range of 0°～60°. With the increase of carbon content, the degree of polarization can be increased too. The degree of polarization of the anthracite with a smooth surface is greater than that of the anthracite with a rough surface. The degree of polarization can indicate the proportional relation between the specular reflection component and the diffuse-reflection component in the reflected light. The calculated degree of polarization can show the inherent nature of anthracite and quantify the relation between the polarized reflectance and the bi-directional reflectance more minutely.