Abstract: The relationship between torrential rain and drought/flood of flood period is analysed based on the daily rainfall data of last 100 years in Beijing. It is shown that the frequency and intensity of torrential rain are important for the amount of precipitation in flood period (June ~ August). In three kinds of torrential rain indexes, the number of equivalent torrential rain day has best correlation with drought/flood grade. It is discussed on the necessity that short-range climatic prediction of drought/flood should combine with short-range climatic prediction of torrential rain process.