Abstract: The whole velocity and turbulence fields in a liquid liquid hydrocyclone with double cylinder and single cone were diagnosed with atwo dimensional LDV system under five testing conditions. The resultsshow that fluid flow in the hydrocyclone is a very strongly swirling turbulent flow. The fluid flows in tangentialdirection are composed of inner and outer swirling flows. The tangential velocity in the inner region is in accordance with therelation of Rankine's forced vortex . The flow field in theouter regi...