Abstract: The cavitation flow fields of a speed high micro centrifugal pump are numerically analyzed.Simulations of the flows at three different flow coefficients are performed.Distributions of vapor,static pressure and relative velocity in the rotation surfaces of the centrifugal pump are presented and analyzed.The results show that vapor bubble is firstly observed to form near the leading edge of the suction side of the blades when cavitation occurs.As the cavitation number is reduced,the vapor bubbles grow in size along the suction side of the blades and extend in the streamwise direction in the flow passages and the cavitation is found to be asymmetric about the axis.By comparing the vapor volume fraction distributions at different flow rates,cavitation is easier to occur at a larger flow-rate.As the inflow total pressure decreases,a significantly low speed zone is observed at the suction side of each blade.Meanwhile,because of the clogging of vapor near the suction side,the local high speed zone behind the trailing edge is observed to expand reversely to the blade passages.In the suction side of the blades,the maximum value of the vapor volume fraction appears near the hub,while in the pressure side,such peak values are seemed to occur near the leading edge and close to the impeller shroud.Cavitation flow in a high speed micro centrifugal pump is initially understood.