Based on the observational data of raindrop size distributions (DSDs) from Parsivel optical disdrometers in Qixian and Jiexiu of Shanxi Province during the period of July and August 2008, a contrast about the characteristics of DSDs and the statistical probability of radar parameters are provided. And then, the dependences of rainfall R and rainwater content W related with reflectivity Z upon axis ratio are discussed. It shows that as the rainfall (R) increases, the corrected R is improved, especially when R>5 mm·h-1. As reflectivity Z is proportional to the 6th power of diameter (D), the corrected reflectivity (Zcorr) is changed much more quickly. At last, on the basis of axis ratio, the Znoncorr-Rcorr relationship and the reflectivity Z and rainwater content W relationship (Z-W) offer a scientific ground for radar measurement of precipitation and a deep-going way research on cloud micro-physical processes and the effects of thunder-lightning on regional precipitation is determined.