The underwater polarimetric imaging target enhancement technique based on unpolarized illumination is proposed based on the physical model of image degradation caused by light absorption and backscattering by particles in water. The advantage of this technology is that the unpolarized light ensures that there is always a difference in polarization between the target reflected light and stray light. And, the characteristic parameters of angle of polarization is used to ensures the accuracy of estimation of stray light intensity. Compared with the current underwater polarimetric imaging techniques based on polarized illumination, the proposed method has wide application range and high image recovery accuracy. Experimental results show that the proposed method can effectively improve the visibility and contrast of underwater images, and the contrast is increased by at least 100%. It is suitable for water bodies with different material targets, different imaging distances, and different impurities and turbidity levels. It has potential application in the underwater imaging field.