The oil-water separator is used to separate the water and oil in the Compressed air, and the Compressed air is purified preliminarily. An oil water separator works by separating oil and water droplets with a density ratio of Compressed air by a dramatic change in flow direction and velocity as the Compressed air enters the separator. After the Compressed air enters the separator shell from the inlet, the airflow is first hit by the baffle plate, and then reverts back down and then back up again, creating a circular rotation. In this way, the water drops and oil drops are separated from the air and settled at the bottom of the shell under the action of Centrifugal Force and inertia force.