Abstract: Based on the coupling numerical solving method, the velocity distribution and flow behavior of Ar in a ladle furnace lid was calculated and analyzed by numerical simulation. The results show that the appropriate off-gas pressures in the periods of emerged arc and submerged arc are -200- -250 Pa and -120 Pa, respectively. When the bottom blowing rate is very small, argon cannot disperse on the top of the molten steel surface; as the Ar-bottom blowing rate increases to 20-50 m³·h^-1, argon can be dispersive and its flow distribution is similar near the molten steel surface, which is in favor of retaining inactive gas Ar. With the augment of the distance from the molten steel surface to the top ladle edge, the circulating region of Ar enlarges on the top of the molten steel surface, which is in favor of avoiding the increase of[O] or[N] in molten steel.