A new type of rotary hydrocyclone for oil-water separation was presented. Its performance was studied by using blend oil-water and kerosene-water systems. The results showed that this rotary hydrocyclone was superior to the static one. Its maximum efficiency was raised significantly. Its operating range was 2 times of that of the static one. Its overflow rate at maximum efficiency was about 1.25-2 times of that of the static one.