Abstract: For low frequency spaceborne Synthetic Aperture Radar (SAR) systems, the ionosphere will have a significant effect on SAR calibration. In this paper, an approach for ionospheric effects correction on spaceborne SAR calibration based on Active Radar Calibrator (ARC) is proposed. The range-displacement induced by ionosphere group delay and the degradation of the range resolution resulted from ionosphere dispersion effect are analyzed, and the effects are corrected by using the width change of the transmitted pulse measured by internal calibration and ARC. The imaging results of ARC before and after correction from simulation are presented. The results show that image quality in range is improved greatly after correction and the approach is proved to be valid.