[Objective] The applicability of HBV model to the runoff sequence simulation of Fuchun River basin was investigated, and the critical disaster-causing surface rainfall of the water level at all levels of the basin was determined through the relationship between water level and runoff in order to provide a service product for the storm disaster risk warning and evaluation and an important basis for the production scheduling of Fuchunjiang Reservoir.[Methods] Taking Fuchunjiang hydropower station as a study area, the meteorological data and HBV hydrological model of the study area were applied.[Results] ① Application of the HBV hydrological model in simulating Fuchunjiang river basin runoff, in a sequence of regular rate and validation period, showed an agreement between the simulated and measured distributions of runoff process. There also was a good relationship between the runoff peak area and live distribution of heavy precipitation. Besides, the mean relative error between the simulated and measured flood peak is less than 5%, indicated a good performance carried out by the calibrated HBV model in the study area. ② Based on the response relationships among the precipitation, runoff, and water level, the warning water level of reservoir and critical surface rainfall could be determined.[Conclusion] The HBV hydrological model performed well to a certain degree in the study area. The reservoir can make a scientific regulation in water level according to the forecast information of rainfall and runoff, when the critical surface rainfall is predicted.