Abstract: In order to solve the problem that traditional casing treatment increases the stall margin while reducing the efficiency of compressor,five innovative non-axisymmetric casing treatments with different circumferential treating angles were designed in this paper.In a series of experiments,the stall margin of a compressor increased with the rise of circumferential treating angle,while the isentropic efficiency rose up firstly and fell down later.It was interesting that the stall margin and efficiency of the compressor were both enhanced when the circumferential treating angle of the non-axisymmetric casing treatment was 120°,the reason of which was simply attributable to the fact that non-axisymmetric configuration changed the unsteady tip flow in the compressor.