Abstract: Based on similarity theory,the 1:4 water model was established for a 100 t ladle in a steel plant,the effect of different positions of bottom nozzle and gas flow-rate on mixing time and slag entrapment was studied by water model experiments. The results showed the mixing time for single nozzle was short when nozzle location distance from center of ladle bottom was between 0.5R and 0.65R; the mixing time was short for double nozzles with location 0.5R and angle of 180°. The mixing time with single nozzle blowing was a little shorter than that of double nozzles blowing when gas flow-rate was same. In order to reduce wall erosion,the nozzle distance from the center of the bottom of ladle should be less than 0.65R.It was concluded that the best blowing argon flow under this experimental condition was 426 L/min,the critical entrapped slag flow was 142 L/min for single nozzle,while 213 L/min for double nozzles,the flow benefitting steel slag interface reaction should be more than 284 L/min.