The environmental trace gases monitoring instrument (EMI) launched on the Gaofen-5 satellite on May 9, 2018 is a high-resolution imaging spectrometer in the UV-visible band. In order to investigate its on-orbit spectral performance, the wavelength peak searching method was first adopted, namely, the solar Fraunhofer line was used as the characteristic peak to quickly obtain the spectral range of the load, then the spectral curve value of the load space dimension was obtained by using the spectrum-matchingmethod, and finally the spectral fitting method was used to obtain the change of spectral resolution. By comparing with the standard Fraunhofer, the peak searching method can find the characteristic peak and obtain the standard wavelength of the peak andthe corresponding pixel, and then the corresponding relationship between pixel and wavelength can be obtained by second order polynomial fitting. The Pearson correlation coefficient method is used as the criterion for spectral-matching method, that is, the maximum correlation coefficient between two spectral is used as the condition for the optimal matching result, and then the offset value between the measured spectral and the standard spectral is obtained. The calibration result satisfies the requirement that the calibration precision is higher than 0.05nm. The spectral fitting method can analyze the change of spectral resolution by solving and fitting the measured spectrum with the high-resolution solar reference spectrum. The analysis results of the all-day 15-track data on January 7, 2019 show that the change of spectral resolution is consistent within a day, and the single row standard deviation is less than 0.01. Therefore, it is of great significance to analyze the performance decay of the instrument in the case of long-term operation or interference.