Based on rainfall products with high temporal and spatial resolution, the RainyDay rainstorm generator was used to generate design rainfall with different temporal and spatial distribution scenarios and rainfall duration. The response law of peak runoff to rainfall temporal and spatial heterogeneity was simulated and analyzed through the distributed hydrological model GSSHA, combined with the covariance analysis method and the constructed rainfall temporal and spatial heterogeneity index system, and the effects of different spatio-temporal heterogeneity indexes of rainfall on peak runoff were studied quantitatively. The results show that the coupling of short time series(2008-2016)grid rainfall data and RainyDay rainstorm generator can generate watershed design rainfall which is similar to the temporal and spatial distribution of actual rainfall. The temporal and spatial heterogeneity of rainfall has a significant impact on the peak runoff, which is greater than that of rainfall duration and rainfall. Rainfall peak coefficient, rainfall concentration and 1h maximum precipitation have a great impact on the peak runoff. The impact of rainfall peak coefficient decreases with the increase of rainfall duration or rainfall return period, while rainfall concentration is the opposite.