Abstract: The features of radar echo and rainfall of cumulus are analysed by using the field observational data obtained in Hunan Province in summer and autumn, 1979—1988. The regression relations of radar echo parameters with the rainfall amount of single station, depth of rainfall, total rainfall amount and rainfall density are then established. The test of such relations using the cumulus rainfall data in Hunan and Guangdong Provinces indicates that they are applicable, to a certain degree, in estimating cumulus rainfall in the vast areas of southern China.