For solving the dual-value problem of RSD raindrop size distribution retrieval algorithm using GPMCO DPR data, a solution is put forward: combining the observation data of S-band weather radar and GPM-CO DPR to provide determinant for the dual-value problem. On the basis of completing the retrieval algorithm, the radar simulation program, Quickbeam, is utilized to validate the algorithm, and actual observation data is utilized to validate the algorithm as well. The results of theoretical validation show that the correlation coefficients between retrieved data and input data are over 0.99, and the results of validation with actual observation data show that the retrieved RSD can reflect the raindrop distribution situation of the rainfall process. The algorithm can help to solve the dual-value problem to o certain degree.