On orbit radiometric calibration based on blackbody is one of the radiometric calibration schemes used in the infrared channel of the Advanced Geosynchronous Radiation Imager (AGRI). Some of the images from long wave infrared channels of AGRI still have some band noise after blackbody calibration, which will affect the image quality. In this paper, the radiometric calibration model of AGRI based on spaceborne blackbody is analyzed, and the concept of spectral response non-uniformity between pixels in the channel is proposed; then, the relationship between the non-uniformity of the spectral response between pixels and the band noise is simulated and analyzed. Finally, based on the analysis results, a method of relative radiometric calibration using a uniform scene is proposed, and the imaging data of AGRI are used to verify the effectiveness of this method to suppress the stripe noise caused by the non-uniformity of spectral response between pixels.