To address the application requirements for relative radiometric calibration and image non-uniformity correction of multi-CCD cameras during on-orbit operations, this study proposes an LED point source-based relative radiometric calibration method for spaceborne systems. Grounded in the inverse-square law of point source irradiance, this methodology employs spatially fixed stable light sources as radiometric references. By establishing a comprehensive technical framework encompassing laboratory cross-comparison calibration, on-orbit calibration coefficient correction, and performance verification, it achieves full lifecycle monitoring and correction of relative radiometric calibration for remote sensing payloads.Through laboratory analysis of the spectral irradiance spatial distribution characteristics of LED point source modules, we established the correlation between light intensity spatial distribution and point source spectral irradiance. This enabled the calculation of spectral irradiance spatial distribution formed by point source modules at the focal plane. Combining with relative radiometric calibration ratios measured by highly uniform integrating sphere light sources, we derived spatial distribution coefficients for the relative radiometric calibration of point source modules. Post-launch secondary correction of calibration coefficients ultimately formed the on-orbit relative radiometric calibration and non-uniformity correction algorithm.Laboratory measurements of irradiance distribution at various imaging positions under different driving currents confirmed system stability with ratio distribution relative standard deviation ≤0.05%, verifying current-independent performance stability. Algorithm validation employed image data with integration times from 8 ms to 16 ms to simulate surface reflectance variations. Post-correction results demonstrated significant non-uniformity improvement quantified by generalized noise assessment: non-uniformity decreased from 1.75% to 0.97% at 8 ms, 1.55% to 0.89% at 12 ms, and 2.28% to 1.28% at 16 ms. A multi-LED combination calibration strategy with energy-level matching enables wide-spectrum multi-level radiometric energy input through established energy-current relationships.System performance tests revealed exceptional stability LED source on-off cycling stability over 30 minutes exceeded 0.08%, with post-irradiation energy variation across all levels below 1%, fully meeting on-orbit stability requirements. This methodology provides an effective solution for real-time radiometric correction of spaceborne payloads, demonstrating significant application value for ensuring reliable on-orbit instrument operation.