<p>The viscosity of refining slag is an important process parameter in ladle metallurgy. This article, based on a specific plant’s steel ladle as a prototype and using ANSYS FLUENT with the VOF multiphase flow model, investigates the size of the slag eye, the surface velocity of the steel fluid, and the distribution of bubbles within the slag layer under different viscosities of refining slag. It also analyzes the evolution process of the flow field of the steel fluid and bubble movement within the ladle. As the viscosity of the refining slag increases, there is a trend for the slag eyes to expand. When the viscosity of the refining slag is 0 Pa·s, the size of the slag eyes is relatively small; when the viscosity ranges from 0.1 to 10 Pa·s, the slag eyes significantly enlarge; at a viscosity of 100 Pa·s, the size of the slag eyes further increases. The surface velocity of the steel fluid initially increases and then decreases as the viscosity of the refining slag rises. The surface velocity of steel fluid measures 0.1315 m/s at zero slag viscosity, reaches above 0.4 m/s within the 0.1 to 1 Pa·s viscosity range, and declines below 0.3 m/s at both 10 Pa·s and 100 Pa·s viscosity. Bubbles within the slag layer are mainly concentrated at the edges of the slag eyes. The eddy viscosity is high at the slag eyes and decreases with distance from it.</p>