The current study focus on the flow characteristics and the effects of scrap on the bath flow with the help of mathematical model which is built based on the physical model of a 250 t converter. The results showed that the mixing time was a decreasing function of the flow rate of bottom blowing when the flow rate was relatively low (<40 L/min). On the contrary, excessive high flow rate of the bottom blowing would not contribute on the decreasing of the mixing time which demonstrated that increasing flow rate was not favorable for decreasing the mixing time if the flow rate was higher than the critical value. With increasing the scrap volume, the plume formed in the bottom blowing moved towards to the bath wall. Meanwhile, the maximum velocity of the plume increased from 0.24 m/s to 0.40 m/s when the bottom flow rate was 50 L/min compared to the flow rate of 15 L/min. The kinetic energy of the bath was increased while the volume ratio of the low-velocity zone was decreased when the scrap volume increased. The volume ratio of the low-velocity zone can be decreased 89.46% when 40 t scrap was added into the bath compared to that of no scrap addition. Specifically, compared to that of 15 L/min when 60 t scrap was added, the transfer indexes decreased 2.98%, 6.27% and 8.68% when the bottom flow rate increased to 25, 40 and 50 L /min, respectively. The effects of the scrap volume on the energy transfer index was also investigated and the results showed that increasing the scrap volume was benefit to increase the energy transfer index for the bath and large volume of the scrap greatly increased the energy transfer index. When the bottom flow rate was 25 L/min, the energy transfer index increased 2.48% and 41.41% when the scrap volume increased to 10 and 60 t, respectively.