Abstract: Local fluid flow and mass transfer in a converter bath were studied by a cold model. According to the conductivity measured in different regions, the local mass transfer and mixing effect were determined in the bath by using different lance nozzles, lance heights and bath shapes. The effects of the three factors on the mass transfer, dead volume distribution, mixing time and velocity uniformity were analyzed. It is found that the dead volume mainly lies in the bottom near the sidewall and the vortex heart for a standard bath (diameter-to-depth ratio=3.1), but does in the sidewall region for a shallow bath (diameter-to-depth ratio=5.2). Increasing the inclination angle of the lance nozzle and the ratio of bath diameter to depth is beneficial to increasing the circulation radius of the bath, improving the bath flow and reducing the dead volume.