A three-dimensional mathematical model coupling electromagnetic, flow, heat transfer, and solidification has been developed to investigate the effect of eccentric mold electromagnetic stirring (EM-EMS) on the flow and heat transfer of molten steel in round blooms with different cross sections. The uneven distribution of the flow field caused by EM-EMS was improved by changing the straight submerged entry nozzle (SEN) to a four-port SEN. The symmetry index was determined by the velocity distributions on the left and right sides of the center cross section of mold electromagnetic stirring (M-EMS), which quantitatively evaluated the symmetry of EM-EMS on the flow field. In the presence of EM-EMS, the maximum temperature difference of ϕ500 mm and ϕ650 mm round blooms between the inner and outer curves amounted to 63 and 26 K, respectively. The maximum distinction between the solidified shells in the inner and outer curves was 11.5 and 5.3 mm, respectively. After using the four-port SEN, the temperature and the shell distribution on the inner and outer curves for the ϕ500 mm round bloom were almost the same. The symmetry indices of ϕ500 mm and ϕ650 mm round blooms were increased from 0.55 and 0.70 to 0.77 and 0.87, respectively. The four-port SEN can be used to mitigate the negative impact of EM-EMS on the steel flow field.