Abstract: In this paper, the observation data measured by the dual-frequency precipitation radar DPR on board the GPM satellite and the ground-based Ka/Ku dual-band radar CR of the Guangdong Longmen Observatory from April to September 2019 are matched in time and space. Combining with the raindrop spectrum data of the micro rain radar MRR for the CR attenuation correction, we compare the difference of echo intensity detected by DPR and CR, and analyze the systematic differences between the two. The main result are as follows:(1) The distributions of precipitation echoes detected by DPR and CR have similar trends with height. The height of the brightband is basically the same. The echo intensity detected by DPR at the same altitude is significantly greater than that of CR.(2) For non-precipitating clouds, the systematic difference between Ku band and Ka band in CR is about 3.1 dBz.(3) The stronger the rainfall intensity, the greater the thickness of the water film of the CR's radome, and the greater the attenuation of the CR echo.(4) The raindrop spectrum data are used to calculate the attenuation coefficient in the process of bin by bin library correction, and the correction amount of the reflectivity factor of CR in the Ka and Ku bands does not exceed 4 dBz.(5) Integrating all the collocated data, the average systematic difference between the reflectivity factors of CR and DPR after the attenuation correction for the Ka band is 15.7 dBz, and that for the Ku band is 14.4 dBz. Although the systematic difference between the two radars after attenuation correction is still large, these results have significantly improved the data quality of the ground-based Ka/Ku dual-band radar.