Based on the solar diffuser of the satellite calibration spectrometer (SCS), we establish an absolute radiometric calibration model. We can obtain the absolute radiometric calibration coefficient of SCS by processing the on-board diffuser calibration data obtained on December 12, 2018. The radiometric calibration coefficient of SCS is cross-validated thrice using TERRA MODIS, which is used as the reference load. In order to improve the accuracy of spectral matching and to eliminate the difference in spectra setting , the measured equivalent radiance of SCS is interpolated to obtain the spectral radiance, and subsequently the obtained results are integrated with the spectral response function of TERRA MODIS to obtain the predicted equivalent radiance. The comparison results show that the predicted equivalent radiance of each band of MODIS is in consistency with the measured equivalent radiance and the maximum relative deviation is 2.78%, which indicates that the SCS radiometric calibration coefficient is reliable and has a high calibration accuracy. It is verified that the parameters such as bidirectional reflection distribution function (BRDF) and transmittance have relatively high test precision.