Polarization imaging technology under water is a hot spot in the research of underwater imaging. Due to the great attenuation of natural light in water, the underwater imaging system mostly adopts active illumination method. In order to solve the problem that the polarization information of acquired images was biased due to the mismatch of polarization direction between polarization illumination source and polarization detection element in divided focal plane polarization imaging system, which affected the quality enhancement of target images, a light source calibration method for divided focal plane polarization imaging system was proposed. First, the calibration principle of polarized light source was described, then the implementation steps of polarized light source calibration were given. Finally, the underwater target images before and after calibration were enhanced and the image quality was evaluated by using polarized dehazing algorithm and image quality evaluation method. The evaluation results show that the quality of the calibrated image restoration is better than that of the uncalibrated image restoration, and the average gradient can be improved by 2.48 times at most. The proposed calibration method is simple, effective and practical, which is suitable for the calibration of polarized light source in divided focal plane polarization imaging system.