An improved Zhang′s calibration method is proposed, combined with Jean-Yves Bouguet vanishing point calibration method, aiming at improving the accuracy of underwater camera calibration and the establishment of nonlinear mathematical model which has a comprehensive consideration of radial distortion and tangential distortion on cameras underwater. In order to verify the feasibility and robustness of the improved method, underwater calibration experiments are carried out compared with Zhang′s calibration method. The experimental results show that both of the two methods have strong robustness, however, compared with Zhang′s calibration method, the improved one can achieve higher accuracy with smaller reprojection average error and the calibration results are closer to the actual results.