Abstract: The stall margin of compressor can be effectivelyimproved by rotor tip injection, but the available injectors are complex instructure and will increase the engine weight. The purpose of this paper isto explore a new type of injection, which is easy to implement incompressors without increasing the total weight. A casing modification (CM)method was used on the casing near the rotor tip leading edge, so that theaxial velocity near rotor tip leading edge improved, which has a similareffect on the rotor tip injection. The method was numerically tested on therotor 37, and it was concluded that, the CM method could improve the rotorstall margin by 6.7%, and the efficiency and pressure ratio are improvedslightly. Comparison of different schemes of CM method shows that, thelocation of CM influences stall margin most obviously. The analysis of rotortip flow field indicates that, the CM method could increase the rotor tipaxial velocity, push the tip leakage vortex downstream, weaken the blockageat the rotor tip region, and enhance stability of the rotor therefore.