Abstract: In order to improve spectral resolution of an imaging spectrometer without changing its hardware structure, a novel method of spectral refinement was adopted. An imaging spectrometer with liquid crystal tunable filter was used to obtain the approximate spectral data of the incident light for theoretical analysis and experimental verification. In three sets of numerical simulation data, the standard deviations of the spectral intensity difference between the approximate spectra and the true spectral were reduced by 79.3%, 68.3% and 58.8%, compared with the spectra measured with an imaging spectrometer. In two sets of experiment data, the standard deviations were decreased by 84.4% and 60.7%. The results show that the approximation degree between the approximate spectrum and the real spectrum of the incident light is improved and the spectral peaks are separated very well. It is helpful to improve the spectral detection capability of imaging spectrometers.