In order to construct a drought index that can reflects the combined water deficit of river channel water storage, reservoir water storage, and soil moisture content, a standardized watershed water storage index (SWSI) was constructed based on VICFLASH（variable infiltration capacityflexible large scale hydrological routing）model with a resolution of 500 m × 500 m. The reliability and advantages of SWSI were verified through its application in the Qinhuai River Basin to identify historical drought events and analyze drought characteristics from 1980 to 2019. The results showed that the highresolution VICFLASH can well simulate the spatiotemporal distribution of water storage in the basin, with the average relative error of the flow process simulation being 10.6%, and the correlation coefficients between the measured and simulated water storage of six reservoirs in the basin were 0.53 to 0.86. SWSI can accurately identify drought events and reflect the severity of regional drought, with the obtained correlation coefficent between the drought severity and the actual area affected by drought reaching 0.88, and the correlation coefficients of daily SWSI with standardized runoff index and soil moisture anomaly percentage index from 1980 to 2019 were 0.89 and 0.98, respectively. SWSI can not only quantitatively and objectively reflect the deficit state of water storage in the basin, but also describe the spatiotemporal evolution process of drought more objectively.