Abstract: The spectral data of continuous spatial distribution can be obtained by the spaceborne spectrometer, which is widely applied in the detection of terrestrial vegetation and marine environment. In order to correct the distortion of the system, the imaging lens was designed as an off-axis transmission-type optical system. There were three optical axes in the system, the angle between the axes was 0.606°, and the eccentricity was 0.279 mm, which the traditional assembly and adjustment method could not solve this problem. The sensitivity analysis results of the system were obtained by using the computer-assisted assembly and adjustment technology, and a new assembly and adjustment method of multi-reference axis centring was proposed. The reference axis was constructed by presetting the eccentricity and tilt of the structure, and the reference axis was extracted by using an optical plate. The complex multi-axis system was decomposed into the single-axis subsystem, and the multi-axis transmission system assembly and adjustment of the spectrometer was accomplished. The test results show that the lens eccentricity error is less than 25.4 μm, the tilt error is less than 17.7″, and the distortion deviation between test results and theoretical results is less than 0.32 μm, which provides a new way for assembly and adjustment of off-axis refraction lens.