In the peripheral scanning imaging system,it is necessary to eliminate image rotation through specific optical components.The Pechan prism is one of the most commonly used derotation elements.Because the angle error of the prism has a greater influence on the optical axis of the system,the requirements for the angle error of the Pechan prism are very strict.The vector form expressions of reflected light,refracted light and rotation of the three-dimensional coordinate system are derived in the paper.Then the angle error analysis model of the Pechan prism is established.On this basis,the direction vector of the exit optical axis,which after the incident optical axis is refracted and reflected by the Pechan prism,is analyzed.The direction vector of the optical axis emitted from the Pechan prism and its deviation relative to the incident optical axis are calculated based on Matlab.By comparing with the ray tracing simulation results and experimental results,the correctness of the established model and the analysis and calculation process is verified.The problem of four crosshairs in the prism bonding process is explained,which has a guiding role in the processing of the prisms.At the same time,the gluing efficiency and the accuracy of the optical axis consistency of the prism are improved.