A method for phase separation of oilwater twophase fluids in a pipe was described. The numerical simulation of oilwater twophase flow with different types of cyclones and different inflow parameters was carried out. The result shows that the swirl angle of the optimized swirler is 45°.It is observed that the phase separation characteristics are well approaching the ideal condition with the oil superficial velocity is below 0.20 m/s and water superficial velocity is in 0.25~0.8 m/s.The experimental results which agree well with the simulation also show that the static cyclone device can successfully be used to realize phase separation. The phase separation method may provide an innovative approach to the measurement of phase holdup, the process of water reinjection and mass transfer of multiphase flow.