The process of ladle turnover in "one ladle to an end" mode was abstracted as three serial and nearly closed queuing systems with system capacity constraints, i.e. BF iron tapping, desulfurization and BOF iron charging queuing system. A calculation model of theoretical turnaround number of hot metal ladle based on the queuing theory with limited system capacity was proposed. Theoretical turnaround number of Chongqing Iron and Steel Co., Ltd. was calculated by adopting proposed model, and the results are:294 min for turnaround time of ladle reaching statistical balance; 17 theoretical turnaround number of ladle. Research shows that optimizing the system capacity should be a crucial step to reduce the turnaround number of ladle. The main measures of practical production lie in improving the distribution strategy of empty ladle and strengthening the coordination between iron-making and steelmaking process, et al. Corresponding parameters are obtained by adopting the calculation model, i.e. 260min for l turnaround time of ladle; 15 theoretical turnaround number of ladle.