The XINRAD S/B radar was put to use after 2004 in Guilin, and some experiments on radar rainfall estimates were carried out. A mixing scanned plane was defined according to the actual situation of Guilin, by means of the graded radar echo intensity and the optimization method， the coefficients of 〖WTBX〗A〖WTBZ〗 and 〖WTBX〗b〖WTBZ〗 in〖WTBX〗 Z〖CD*2〗I〖WTBZ〗 relation are obtained. The capability of measuring rainfall quantitatively is improved obviously. The accuracy increased by 20% in use of our〖WTBX〗 Z〖CD*2〗I〖WTBZ〗 relation, compared with the method of weather system classification; increased by 40% compared with that by the generally used one developed by US. Using the graded radar echo intensity to set up the 〖WTBX〗Z〖CD*2〗I〖WTBZ〗 relation for radar rainfall estimates is easy to operate, to change the 〖WTBX〗Z〖CD*2〗I〖WTBZ〗 relation automatically, and to achieve the automation of rainfall estimates.