Abstract: This work applies a hydrodynamic model to simulations of urban rainfall-runoff process to examine the effect of a lake in controlling urban flood inundation, focusing on peak volumes of inundation and severely inundated areas under the conditions of different rainfalls, different lake areas, and different lake locations. The results indicate that as the lake area centered at the same location is reduced from 0.502 km2 to 0.00785 km2, the peak inundation volume is increased by 12.7% - 18.2%, and the severely inundated area increased by 11.7% - 25.7%. Lake location plays an important role in determining flood inundation. This is demonstrated by the typical condition of a storm of 100 year return period and a lake area of 0.5024 km2, in which the severely inundated areas are 0.173 km2, 0.169 km2 and 0.163 km2 in the three cases of the lake located in the river’s upper, middle and lower reaches respectively, indicating more effective control of a downstream lake on the surface runoff that causes urban inundation.