The onshore oil water separator has the advantages of compact structure, simple operation, convenient management, high separation efficiency, and low energy consumption. The treated water can be directly discharged or appropriately reused, and the extracted waste oil can be directly reused. The device organically combines enhanced gravity separation, coarsening, and adsorption coalescence processing processes into a steel cylindrical overall structure, and combines with infusion pumps, oil storage tanks, and electronic control boxes to form a processing device. The treatment process fully utilizes the characteristics of gravity separation and the characteristics of different separation materials, thereby having a wide range of adaptability to various oily wastewater conditions that are difficult to treat. It is suitable for the treatment of oily wastewater from various types of oil products without surfactants. The device organically combines enhanced gravity separation, coarsening, and adsorption coalescence processing processes into a steel cylindrical overall structure, and combines with infusion pumps, oil storage tanks, and electronic control boxes to form a processing device. The treatment process fully utilizes the characteristics of gravity separation and the characteristics of different separation materials, thereby having a wide range of adaptability to various oily wastewater conditions that are difficult to treat. It is suitable for the treatment of oily wastewater from various types of oil products without surfactants.