Abstract: Five kinds of skew grooved cases with different geometric parameters were designed and tested on a rig of single stage axial-flow compressor.The detailed measurements of the overall performance and element performance,especially the blade tip flow prove that the treated casings enhance the compressor efficiency,but make slight loss of stall margin.According to analyzing the effects of each structural parameter on the compressor efficiency and stall margin,an optimization of primary geometric parameters has been found out.Then the effects of the grooved casing treatments on the performance of the compressor rotor have been revealed and some valuable conclusions have been reasoned out.