Abstract: Hydrocyclone tester used for oil-water separation was set up.The pressure characteristics and separating performance were researched.Under the condition of the feed flow is 2.9 m~3/h and the pressure drop between inlet and overflow is 0.21 MPa,the water content can decrease from 5%~8% to less than 0.45% and mean dewatering ratio is about 90%.The efficiency is not obvious when 160 mT magnetism was used to intensify hydrocyclone separation.