Abstract: To solve problems such as short hydrological series, coarse parameterization, and insufficient engineering validation in design flood review for medium-sized reservoirs in Karst regions, it takes the Shangshui Reservoir in Bozhou District in Zunyi City of Guizhou Province as a case. Based on 61-year long-term rainfall data (1960-2020) and spring water level observations, it optimized parameters of the rainfall-runoff method and established an integrated review framework encompassing the rainstorm frequency analysis, the flood routing calculation, and the dam safety review. Results indicate that extending the rainfall series narrowed the 95% confidence interval of extreme rainfall from ±8% to ±3%. The confluence coefficient was revised from the initial design value of 0.32 to 0.335; under the check flood condition, the maximum spillway discharge reached 305m³/s, with a dam crest freeboard of 0.743m. After curtain grouting, the dam foundation permeability decreased from 12 Lu to 1.8 Lu, and the dam abutment stability safety factor increased by 9.6% compared to the initial design.