Abstract: To investigate the risk characteristics of urban flooding in Kunming′s central urban area, a combined GIS database and SWMM model was developed to simulate surface runoff under different return periods. The study analyzed runoff risk, total runoff volume, peak flow variations, and the impact of underlying surface conditions. Results showed that total runoff, peak flow, runoff coefficient, and runoff depth increased with longer rainfall return periods and higher impermeable surface ratios. Under various return periods, severe flooding risk primarily occurs in central and southern areas. At a 5-year return period, low and low-medium risk zones accounted for 10.56% and 68.83% respectively, while medium-high and high-risk zones rise to 72.49% and 24.25% at 100-year return periods. Rainfall intensity and volume significantly influenced runoff processes compared to surface characteristics. To mitigate flooding, measures like optimizing green space layouts, upgrading drainage systems, and installing retention ponds in low-lying areas were recommended. These findings can provide references for Kunming′s prevention of flooding.