<p>Casing treatment has been demonstrated to effectively enhance the stall margin of compressors. In this paper, the effect of variations in circumferential groove parameters on the performance of supercritical carbon dioxide (sCO₂) centrifugal compressors is investigated. The comparative analyses showed that casing treatment is more effective when the circumferential grooves are placed in areas of separation vortices, which will significantly reduce flow separation. Among the circumferential rectangular grooves with varying structural parameters, the maximum stall margin improvement is 5.17%. Based on the flow characteristics inside the rectangular grooves, a new design featuring circumferential circular grooves is proposed. A comparison between circular and rectangular grooves revealed that the circular groove offers superior performance, resulting in a better improvement in groove flow and stall margin. The maximum stall margin improvement reaches 13.8%. This study utilizes numerical simulations to investigate the effect of circumferential groove casing treatment on the performance of centrifugal compressors.</p>