This paper selects three different types of rainfall processes triggered by three typhoons in the Meixi Basin in 2012, “Saola”, 2014 “Hagibis”, and “Nepartak” in 2016, and explored the effects of radar rain measurement and nowcasting. Application prospects of hydrological forecasting in small and medium watersheds. Using 24h accumulated rainfall relative error RE, the ratio of the root mean square error of the two dimensions of time and space to the mean value of the corresponding dimension m-RMSE, the average absolute error RMAE and the average deviation RMB and other indicators, based on the observation value of the ground rainfall station to evaluate the radar rain measurement and 1h The results of ensemble nowcasting in the forecast periods of, 2h and 3h show that the radar rain measurement is generally close to the observation value of the ground rainfall station, and the RE values of different types of rainfall are all around 3%; rainfall with uniform temporal and spatial distribution has excellent nowcasting effects For short-duration rainfall and heavy rainfall nowcasting, and with the extension of the forecast period, the effect of uniformly distributed rainfall in time and space is more stable, and the forecast accuracy of short-duration rainfall and heavy rainfall is significantly reduced. Therefore, radar rain measurement and nowcasting with high temporal and spatial resolution have good application prospects in hydrological forecasting of small and medium watersheds, but short-duration rainfall and heavy rainfall need to be further studied.