Abstract: Nine kinds of circumferential grooved casing treatment structures were designed by the orthogonal experiment's requirement.Optimized experiments of the geometry structure of circumferential groove were performed on a single stage subsonic axial compressor with the nine kinds of circumferential grooved casing treatment structures at two rotor speeds.The results of orthogonal experiments show that the orthogonal experiments are successful.It is not necessary to test all casing treatment of possible combination of structural factors.The structural factors of casing treatment were forecasted successfully by analysis of the orthogonal experimental results with orthogonal analytic method and the subsonic rotor gains the best stall margin improvement with this kind of circumferential grooved casing treatment of possible combination of structural factors at two rotor speeds.