A combined device was designed for the treatment of substation oily wastewater based on gravity oil-water separation method and filtration method, a special research and development materials-polyurethane sponge was used in the oil-separation zone. The dynamic process of oil-water separation of different rations of oil-water in the device was simulated by finite element analysis, and the oily wastewater from a substation in Zhejiang province of China was treated. The corresponding results are listed as follows: the FEA simulation results showed that the oil-water separation effect is the best in the oil separation zone, and the separated oil body accounts for more than 90%; the experiment showed that the removal rate of COD reached 99.45% after treatment by the device, which meets the first-class sewage discharge standard. In addition, the polyurethane sponge material carried had good hydrophilic and oleophobic properties and excellent regeneration and recycling performance.