The technology of underwater polarization difference imaging can significantly suppress the backscattered light, the key factor affecting the quality of underwater imaging. Therefore, it is an effective method to obtain clear images in the underwater scattering environment. Traditional polarization difference methods are based on the polarization images at two orthogonal polarization directions and have obvious effects on suppressing the backscattered light. However, the corresponding degree of modulation freedom is low, which limits the further improvement of imaging quality. To solve this problem, we proposed an improved method of underwater polarization difference imaging in this paper. After the difference of polarization images in two optimal polarization directions and the introduction of the weight coefficient for the difference item, this method could realize the underwater polarization difference imaging with three degrees of freedom. The experimental results show that compared with the traditional polarization difference imaging, the proposed method can better restrain the backscattered light, highlight the signal light of the objects, and finally achieve the underwater clear imaging with higher quality.