Based on the principle of similarity, water modeling experiments were carried out for a 150-t ladle furnace. The rational parameters of argon stirring were determined as the optimized positions of nozzles, top area of the porous brick, and gas flow rate. The following results are obtained: 1) the optimized positions of two nozzles are at 0.333R (R refers to the radius of the ladle at bottom) with an angle of 135°; 2) the top diameter of the porous brick should be 130 mm; 3) the flow rate of gas should be 25.0-30.6 m3/h. The plant trial shows that the improved process is effective in enhancing the cleanliness of round billets. The total oxygen content, microinclusions, and macroinclusions in round billets are reduced by 12.5%, 8.2%, and 20%, respectively.