Abstract: Based on the similarity principle, a water model was established for the problem that a large number of bubbles overflow from the submerged tube in the CAS process. The effects of the flow rate of bottom gas, the submerging depth of the submerged tube and the nozzle position on the mixing behavior of liquid steel were studied. It is found that the problem of bubble escaping can be resolved when the hood center and the bottom nozzle center are coaxial. For a 300 t ladle, the optimal bottom blowing process was obtained. The optimal position of bubbling is 0.3r to 0.4r (r is the ladle bottom radius) away from the ladle bottom center, the flow rate of bottom blowing is approximately 600 L·min^-1 in the refining process and 500 L·min^-1 in the deslagging process, and the immersion depth of the submerged tube is 180 to 225 mm. Industrial tests show that the improved bottom blowing process can effectively prevent bubbles from overflowing, and improve the cleanness and castability of the LCAK steel.