Recently, climate change and urbanization have been caused by urban flood. To mitigate flood, there are structural measures such as detention reservoir and pump station and non-structural measures such as pump operation rules and gate operation rules. However, structural measures cannot cope with rainfall stronger than design rainfall intensity and need to construct to develop flood mitigation capacity. Urban drainage system needs non-structural measures that maximize the efficiency of structural measures. The efficient operation of the pump as one of non-structural measures can develop the discharge capacity of urban drainage system to prevent urban flood. In this study, we proposed advanced optimal pump operation at Mokgam stream located Seoul and Gyeonggi-do. Advanced optimal pump operation is considering the water level of the vulnerable points and the water level of reservoirs. Risk of flooding is predicted by the water level of vulnerable point and reservoir. Therefore, pump station is able to proactively start the pump compared to the current pump operation, reservoir secures free space to develop flood mitigation effect and discharge capacity.