In recent years a new technique has been developed which uses aground-based radio meter as a supplement for a radar in quantitative lymeasuring rainfall. Two kinds of joint systems of radar-radiometers of 8 mm and 3.2 cm wavelengths were set up in 1980 by the Institute of Atmospheric Physics, Academia Sinica. A solution scheme for the measurements given by one of the systems is proposed. By means of numerical experiments. the above scheme for 3.2 cm wave lengths and two others for the systems by use of radar only are examined andcompared. And errors caused by various factors of these methods are discussed. Some significant results are obtained concerning the feasi-bility of the methods used.