The storm drainage system model of Xincheng Park in Guangming New District of Shenzhen was set up based on InfoWorks ICM model. In this study the catchment area was divided respectively according to manhole and gully, and its effect on flow simulation results of park outlet was analyzed. The results showed that the selection of node-type had no obvious effect on peak flow simulation result in the condition of light or medium rainfall, while for storm or heavy rainfall the selection of node-type had great influence on peak flow. Compared to catchment division based on manhole, runoff-yielding time producing was delayed by dividing the catchment area based on gully. Therefore, research goal, regional scale and rainfall characteristics should be considered in the process of modeling to reasonably divide the catchment area.