Spatially modulated imaging Fourier transform spectrometer (SMIFTS) was different from other spectrometers. It gained one dimensional spatial information and one dimensional spectral information. Calibration of spatially modulated imaging Fourier transform spectrometer was imperfect for its special theory. A method of radiometric calibration is introduced, which used spatially modulated imaging Fourier transform spectrometer and spectral radiometer to collect irradiance of the same target. After converted interferograms into spectrum and compared with the true spectrum collected by spectial radiometer, calibration coefficients were obtained and the calibration accuracy was analysed. The results indicated that the method can satisfy the requirement of spectral radiometric calibration by spatially modulated imaging Fourier transform spectrometer, the calibration accuracy reached 5.74％.