Kota Lama Semarang was an area where had land subsidence ± 5 cm/year. It made the land surface elevation of Kota Lama Semarang is lower than sea water level and river water levels. It made flood and tidal flood happened in Kota Lama Semarang. The problem was treated by applying polders system drainage (non-gravity systems). The Final report aimed to protect Kota Lama Semarang from flooding by applying design polder system with its components, namely: retention ponds, primary canals, pumping stations, discharge channels, and dikes. The methods included: field surveys, problem identification, problem definition, literature review, data collection, analysis of hydrological data, technical for all components, the calculation of project cost and the time schedule, the stage of the Work Plan and Technical Requirements, and manufacturing method of the project.The polder system is planned retention pond for 18363.25 m3 capacity, 6105 meters of primary channels using precast, three pumps with each pump has 0.5 m3 capacity, 550 m of long exhaust duct using steel pipes, and 30 cm of highly the elevation road that used as embankment on Parks Tawang st., Peacock st., Cenderawasih st., Tantular masters st., Sendowo st., and KH. Agus Salim st. The cost to build this polder system is Rp 34,858,000,000.00. In the construction, it have to be known time schedule and traffic management, because the area has densely residential areas and has enough traffic flow congested. Beside of calculating the technical, it is needed to socialize with local citizen in order to participate in the maintenance of all components of the system so the polder system drainage can be used optimally and persist throughout the life of the plan