Abstract: An axial-flow compressor rotor was tested in detail with a solid casing and three types of skewed slot casing. It has been found that skewed slot casing has a great effect not only on the over-all performance of compressor, but also on the type of rotating stall, spatial propagation, development of stall cell and the flowfield behind rotor. The experimental results in this paper are valuable to establishment of three dimensional model of rotating stall,the exploitation of new function of casing treatment and the practical application of casing treatment in aviation industry.