Interferograms of the spatially modulated imaging Fourier transform spectrometer can be distorted with the nonuniformity of array sensors,little deviation will result in notable variation in the recovered spectra,so it is very important to calibrate the interferogram and eliminate the nonuniformity of array sensors before recovery.A new method of on-orbit relative calibration for the spatially modulated imaging Fourier transform spectrometer based on radiometric calibration field is introduced without the calibration coefficient in laboratory,it only needs the spectra of a uniform field which covers several lines of CCDs across the orbit,each line of spectra corresponds to a frame of interferogram.Simulation and phase matching is carried out to calculate the calibration coefficient.The result shows that the method can get good performance.After calibration,interferogram has a steady tendency and shows significant streaks away from zero point,eliminating the strips in the recovered spectra.