To estimate rainfall with C-band dual-polarization radar measurements, attenuation correction should be done on radar reflectivity factor because of its easy attenuation by hydrometeors along the path at C-band. Wavelet analysis is employed to preprocess Ф_DP for generating K_DP based on data fitting result, and K_DP is thereby used for attenuation correction. Validation of attenuation correction is executed by comparing pixel-to-pixel the reflectivity factor of a S-band radar with that of C-band radar before and after attenuation correction. The corrected C-band radar reflectivity factor is getting close to that of S-band radar. For rainfall estimation, different schemes lead to diverse results. Rainfall amount estimated from S-band radar is more reliable than that from C-band radar if corresponding Z-R relationships are used. But estimation from C-band radar by using R (Z_H,K_DP) relation with attenuation correction becomes better than that of S-band radar by using R (Z) equation. Gage-adjustment is necessary in case of rain-rate over 10 mm·h^-1. After adjustment, the low-biased radar estimation is calibrated, and the gap between radar estimation and gage measurement goes down.