This paper conducts numerical trade study of the axial groove (AG) casing treatment for micro-compressor actuators used for Co-Flow Jet (CFJ) active flow control. The purpose is to increase the stall margin for the micro-compressors while minimizing the design point efficiency penalty. Three geometrical parameters are varied for the trade study, including: width, length and skew angle. The numerical approach is validated with a tested micro-compressor using recirculating casing treatment. A very good agreement is achieved between the predicted speedlines and the measured results for the validated micro-compressor. For the width study, wide width with W/P of 60% possesses a higher stall margin improvement (SMI) of 10.1%, but an increased design point efficiency penalty of 4% also occurs. To preserve micro-compressor efficiency, the width W/P of 30% is adopted that has SMI of 3.1% with efficiency reduced by only 1.1%. Decreasing AG length to 0.7C (chord) results in a reduction of efficiency penalty while maintaining a similar SMI. However, a further decrease of AG length to 0.6C significantly hurts stall margin and reduces SMI by half. For the skew angle study, 52.5◦ is the optimal angle for AG to extract tip flow, which substantially enhances flow re-circulation and mitigates tip blockage. Overall, the optimum AG has the upstream point located at 0.2C ahead of LE and downstream point at 0.5C after the LE and has a W/P of 30%, a length of 0.7C with a skew angle of 52.5◦. The micro-compressor with the optimum AG configuration is able to improve stall margin by 7.4% with a design point efficiency penalty of 0.6%.