Abstract: The C-band Frequency Modulation Continuous Wave (C-FMCW) vertically pointing radar was developed with a newly signal processing technology. The C-FMCW radar uses the two-dimensional FFT signal processing technology, with the lowest detectable echo power of -170 dBm, and the quantitative calibration is difficult for weak signal. For a standard signal source analog echo point frequency, its frequency signal is able to be broadened to the signal with the same scanning range as the radar system, to get the calibration curve with the minimum input power up to -169.77 dBm, in which the calibration curve inflection point is able to confirm that the radar noise power is about -168 dBm. The spectral density of reflectivity can be computed from the spectrum of quantitative calibration. The data observed from the C-FMCW radar are compared with the SA scanning radar on Dingyuan, Anhui Province from June of 2013. The comparison analysis uses the data from the 48 km and 83 km CINRAD/SA Bengbu and Hefei radar, respectively, for the August 24 precipitation event. This event includes the two stages with convective cloud and stratiform cloud respectively. The reflectivity vertical distributions in the stratiform cloud for the C-FMCW radar and CINRAD/SA weather radar are basically in agreement, showing that the calculation of the C-FMCW radar system is reasonable. The average difference between the C-FMCW radar and SA radar in Bengbu in terms of the root mean square difference is 1.75 dB, and that between it and the Hefei SA radar is 2.02 dB. A preliminary analysis using the products and the spectral density of reflectivity, shows that the C-FMCW radar has a good prospect in the identification for the different particle phase thickness in precipitation cloud body, the study of echoes in the boundary layer of the clear atmosphere. And, it can also help to recognize the strong variations of vertical motion in the severe rain clouds.