As a kind of ultraviolet-visible imaging spectrometer, the environmental trace gases monitoring instrument (EMI) is mainly used to realize the global daily atmospheric trace gas concentration inversion with high spatial resolution. During the on-orbit operation, the performance of EMI tends to decay with time due to the influence of the spatial environment. In order to effectively monitor its decay condition, the on-orbit temperature is analyzed by using the 0-level data of the load to the ground orbit to realize the long-term on orbit temperature monitoring. By calculating the mean value and standard deviation of the dark background image noise in the satellite points of each orbit, CCD (Charge-Couple Device Detectors) dark background noise variation trend monitoring with time was realized to evaluate further the damage of CCD pixel points caused by space particles. The on-orbit pixel performance and radiation flux of the CCD detectors were evaluated by the response of the internal white light source on the CCD with multiple on-orbit measurements. Using the 0-level solar Spectral data measured by EMI in orbit, combined with the second-order Gaussian Function model obtained from the laboratory test before launch, the Instrument Spectral Response Function (ISRF) is an inversion with the least square method. Real-time on-orbit updating of the instrument’s spectral response function is realized. The on-orbit relative decay factor of the Quartz Volume Diffuser (QVD) and the Reference Solar Diffuser (RSD) were calculated using the Solar spectrum measured many times by the QVD and RSD. The on-orbit decay correction of diffuse reflector plate is realized. The results show that the temperature is stable after the EMI load has been in orbit for two years, the mean annual increase rate of dark background in each channel is about 0.25%~1%, and the fluctuation range of standard deviation of dark background is within 1.5%. The on-orbit ISRF function varies by about 2.3%. The light path response of the internal white light source is less than 1%, and the annual decay rate of QVD is less than 1.75% for the UV2 channel, less than 1% for the VIS1 channel, and less than 0.5% for the VIS2 channel, respectively.