Abstract: A three-hole dynamic probe is reported in this paper which can measure the unsteady flow direction, flow velocity, total and static pressures of a 2-D flow field. Three miniature pressure transducers are mounted in the prode to detect the pressure fluctuation of the unsteaey flow. The dynamic pressure signals are recorded with a digital data acquisition system controlled by an microcomputer. The flowfield in rotaing stall regime of a singl-stage axial compressor can be studied by means of this probe and the system. The distributions of the flow velocity, flow direction, the total and static pressures in the rotating stall cells have been obtained in detail.