An oil mist separator includes a body inside which a filtering chamber is formed for a filtering unit made up with several centrifugal dust collectors. With an air intake unit, the outside oil mist is sent into the filtering chamber. Then, the centrifugal dust collectors are used to cause a spiral airstream. With a centrifugal force caused by the spiral airstream, the oil mist is made to separate from the air. Next, the filtered air of zero pollution is vented to the atmosphere, and the separated oil mist is collected and recycled. Thus, the oil mist may be separated and the recycled oil mist may be made into a low-level oil product or a release agent used in the building industry for achievement of the effect of environmental protection.