High-precision centroid positioning is the key to the geometric calibration method based on a single collimator and a separated two-dimensional turntable. However, the relative response difference of the instrument will affect the centroid positioning accuracy. Therefore, a centroid positioning accuracy improvement method based on the relative response correction is proposed, which can effectively improve the centroid positioning accuracy, thereby improving the geometric calibration accuracy. The laboratory geometric calibration experiment based on the directional polarimetric camera proves the improvement effect of the proposed method. The improvement effect is more significant in the large field of view area, and the maximum geometric calibration accuracy is about 0.1 pixel. Finally, based on the proposed centroid positioning accuracy improvement method, the geometric model parameters of high-precision directional polarimetric camera are obtained in the laboratory, and the model fitting residual is better than 0.1 pixel.