<p>Annular argon bubbling (AAB) process at tundish upper nozzle is a new method of removing fine non-metallic inclusion in tundishes. However, slag eyes caused by the generated gas plumes can bring about an increase of oxygen and nitrogen in molten steel, seriously affecting the quality of steel product. In the present paper, a number of experiments for AAB process was conducted by a one-fourth scaled water model to research the formation and evolution process of slag eye and slag entrament, and the effects of liquid level, slag layer thickness and gas flow rate on the slay eye area were investigated as well. The results show that the area of slag eye increases with increasing gas flow rate, liquid level and decreasing thickness of slag layer. A larger gas flow rate and liquid level generate a larger size bubble and rising velocity of gas plume at two-phase interface. Base on the experimental data, the dimensional analysis method was further used to establish the correlations for divergence angle of gas plume, Sauter mean diameter (SMD) of bubbles and plume rising velocity in terms of the parameters mentioned above, an empirical predicting model for dimensionless slag eye area was obtained by polynomial regression with a determination coefficient <i>R</i>² of 0.91. This model can effectively predict the slag eye area in the tundish with AAB process, providing important technical support for its practical application in industry.</p>