Deluge system is an important system on offshore oil and gas production facility. The design of deluge system is related with other offshore system design such as electric system and general layout design. Nozzle type selection and deluge distribution piping routing have much more impact on the fire water system design. We put forward an optimization method from the theoretical to the actual engineering design aspects. This method can decrease the water demand as much as possible and save the engineering cost on the premise of meeting the requirements of safety and standards.