Abstract: System and method for control of a subsea located cyclone for separating oil from water. The cyclone is arranged to receive water with oil contents through an inlet line, the oil is separated from the water and delivered through an oil outlet to an oil outlet line, and the water is delivered through a water outlet to a water outlet line. The system is comprising a control valve in the oil outlet or oil outlet line from the cyclone, a first differential pressure transducer arranged between the inlet line and the oil outlet from the cyclone, and a second differential pressure transducer arranged between the inlet line and the water outlet from the cyclone. The system is distinguished in that a sensor for measuring oil contents is arranged in the water outlet or water outlet line, and via a control means said sensor is operatively connected to the control valve.