The greenhouse gas monitoring instruments were carried on the Gaofen-5-II satellite, which was launched into orbit from the Taiyuan Satellite Launch Center on September 7, 2021. In order to improve the on-orbit data quantification level, a calibration device based on diffuse reflector system was designed, which can realize on-orbit spectral and radiation calibration. In this paper, the principle of standard spectral line selection is given, and the characteristic spectral lines that can be used for on-orbit spectral calibration are extracted. The wavelength deviation evaluation function is established by using the method of matching the high-resolution reference spectrum after the linear function of the convolution instrument with the on-orbit calibration measurement spectrum, and finally using the Levenberg-Marquardt algorithm to evaluate the function. The optimization solution is the on-orbit wavelength calibration result. According to the above method, the on-orbit calibration data are processed. After calibration, the maximum deviation of the on-orbit spectral offset is changed from 0.133 to 0.009c m -1, and variations in magnitude less than 10% of the spectral resolution for C O 2 (1.57 µm) band have been detected.