Abstract: This paper designs the metal sphere calibration software and conducts the metal sphere calibration experiment based on the ground-based Ka-Ku dual-frequency precipitation radar system using a metal sphere. It provides a detailed introduction to the calibration principles, pre-calibration preparations, and specific procedures, followed by an analysis of the results. The reflectivity factor is calibrated by adjusting the respective Ka-band and Ku-band radar constants based on their experimental results to reduce measurement errors. The results demonstrate that the Ka-Ku dual-frequency precipitation radar system achieves high accuracy in measuring the reflectivity factor. The metal sphere calibration is of critical importance for further enhancing the accuracy of the meteorological radar reflectivity factor.