Abstract: The test centrifugal fan is specially designed and constructed for the non-touch measurement. The centrifugal fan used in this work is entirely made of transparent material. In order to apply PIV technique to measure the flow in the fan，the optical system of particle image velocimetry is set up. The seeding particle is also chose，and the set of the interval between two pulses are described. At last，PIV measurements are applied to measure the flow within the vaned diffuser. The absolute flow field is measured at one operating condition. The experimental measurement results of the flow fields at three different axial position are given. The characteristic of the flow within the vaned diffuser is discussed.

Key words: PIV, Centrifugal fan, Measurement, Vaned diffuser