Reflected lights on object surfaces are composed of specular and diffuse reflection lights. To separate the specular and diffuse reflection lights on a smooth object surface, a polarization state characterization model based on the collaborative effect of specular and diffuse reflections was proposed and was used to analyze the polarization characteristics in a mixed reflection region. Based on their polarization characteristics and their distribution relations perpendicular and parallel to the smooth object surface, the specular and diffuse reflection lights were separated by polarization orthogonal decomposition. According to the correlation features between the specular and diffuse reflection components, the normalized correlation minimum between the specular and diffuse reflection lights and its corresponding to the degrees of specular and diffuse reflection polarization were calculated by the gradient descent algorithm, thus enabling the successful separation of the reflected lights. By testing reflected light images obtained from different scenes, the results indicate that the proposed algorithm could effectively separate reflection lights.