Abstract: The three-dimensional flow field inside the tip region of a low speed large-scale axial-flow compressor rotor at near stall condition was measured with the help of a five-hole conical probe drived by a rotating four-coordinate probe traverse mechanism.Results indicate that,radial migration of boundary layer of blade suction surface is strong,which induces a vortex nearby,flow separation appears on the blade suction surface,a blade scraping vortex exists in the corner of the blade pressure surface,strong mixing occurs between boundary layers of the pressure surface and the suction surface at median part of the rotor passage,which leads to substantial deficits of total pressure and axial velocity.All of these forms a complicated flow field in the rotor tip region.