As the most widely used optical structure, coaxial optical system has become the critical component of many elaborate compound machines. However, with the development of science and technology, aerospace and lithography technology has put forward higher requirements on the imaging quality of ultra-precision coaxial optical system. And the optical axis consistency condition plays a critical role in the system imaging quality. In this paper, the dual optical path system based on light splitting prism is introduced, in which the coaxiality of the dual optical path become a critical issue. For the high coaxiality assembly, the optical centering assembling technology based on optical imaging principle is applied to ensure the coaxiality among the optical axis of optical element, the rotation axis of corresponding machine part and the rotation axis of lathe. According to the optical auto-collimation imaging principle, the visualization and transmission of the main datum of the optical system is completed, which will ensure the datum conversion completed with high precision. Finally, the experiment has been conducted and the coaxiality of the actual dual optical system is better than 0.05mm. © 2023 SPIE.