A Calibration error is among the main causes of errors in the quantitative application of radar reflectivity. In this study, the stable and continue doperation of along-term space-borne radar (Precipitation Radar carried by the Tropical Rainfall Measuring Mission satellite, TRMM/PR) was verified. Reflectivity data from the space-borne radar were converted from Ku-band to S-band. By comparing the reflectivity data gathered from the space-borne radar and Nanjing radarover the same period for different types of precipitation (stratiform or convective) at different altitudes (relative to the position of melting layer, ML), it was determined that there was a high correlation between the two radars' observations and a stable difference in stratiform precipitation below the ML. Further, the regression relationship between reflectivity factor values observed by the PR and Nanjing radar was obtained by comparing and analyzing the reflectivity factors of stratiform precipitation under the ML. Consequently, the regression between the two radar reflectivity factors provided a linear correction which was then applied to the reflectivity of the Nanjing radar. Rain gage data employed to verify this correction revealed that the precipitation estimated using GR reflectivity data with correction was closer to the rain gage observations than without.