Abstract: The turbulent flow field in a Stairmand cyclone separator with and without a reducing pressure drop stick(Repds) was measured with PIV(particle image velocimetry).The velocity,turbulence intensity and Reynolds stresses were obtained.The comparison of these parameters with and without the stick showed that the Repds reduced the swirl kinetic energy and turbulent intensity in the vortex central region of the cyclone.The mechanism of the pressure drop reducing by the Repds was discussed thoroughly.