Abstract: To have an insight into the circulating flowrate and mixing characteristics in RH-PTB vacuum refining process, the relevant system was modeled on a scale of 1:5.5 to investigate the effects of different parameters on the circulating flowrate and mixing time. The results showed that with the increasing bubbles' travel and the liquid level in vacuum chamber and decreasing quantity of liquid steel for refining, the circulating flowrate increases while the mixing time decreases. So, some effective measures should be taken in actual system to increase the circulating flowrate in case the quantity of liquid steel for refining is overmuch for refining. Besides, the expressions of circulating flowrate and mixing time were derived by regression equation with experimental data.