Particle image velocimetry (PIV) technology is widely used in fluid flow measurement. The refractive index difference of the medium causes the light to deflect on the wall of the tube, which may result in image distortion and directly affect the accuracy of velocity measurement. In this article, the physical model of optical refraction is established, and the functional relationship between the object point and the image point in the circular pipe is achieved. Then, the pixel coordinates of the corrected image are obtained. The bilinear interpolation algorithm is used to obtain the pixel gray value to reconstruct the corrected particle image. Finally, the velocity field in the tube is calculated according to the multi-grid iterative algorithm. The static fluid grid image deviation and laminar flow velocity field measurement experiments are carried out respectively. The errors of optical correction box method, linear correction method and distortion correction method based on optical model were compared. The results show that the accuracy of the proposed image correction method based on geometric optics is better than those of the optical correction box method and the linear correction method. The accuracy and effectiveness of the established geometric optics model are fully evaluated by static and flow experiments.