Low impact development (LID) can control the source flow and has been one of the most important strategy to release urban flood disasters. This study used the Stormwater Management Model (SWMM) as a modelling tool to assess the spatial distribution of LID for stormwater runoff control in Gulou District, Nanjing City. The simulation results indicated that: the suitable area of LID accounted for 16.33% of the total area, which have a significant impact on runoff；The net flow coefficient can be reduced by an average of 0.26. With the increase of rainfall period, the efficiency of runoff reduction was decreasing. The flood peak increases with the increase of rainfall intensity and the scale of LID in general. With the increase of rainfall period, the efficiency of flood peak reduction was decreasing slowly. The combination of green roof and permeable pavement has the best cost-effectiveness, while the scheme including bio-detention pool has relatively low cost-benefit. In general, the scheme of green roof + permeable pavement + bio-detention pool + grass ditch has the greatest potential This study can provide decision-making references and case references for LID's spatial planning, sponge city construction and urban storm water management on an urban scale.