Abstract: According to the Maxwell electromagnetic field theory,electromagnetic fields during mold electromagnetic stirring for 240 mm×280 mm bloom casting were simulated by means of ANSYS software.The distributions of magnetic fields and electromagnetic force as well as the effects of string parameters on magnetic field characteristics were analyzed.It is shown that the rotary magnetic field generates electromagnetic force in the mold region,which made molten steel whirl at the horizontal section.The characteristic of the magnetic field along the mold vertical direction was large in the middle and small at the end of the mold.The simulation results of magnetic induction density were consistent with the measured ones.Final,the optimized M-EMS parameters of the current intensity of 350 A and the frequency of 3 Hz for 45^# steel blooms were proposed and the results indicates that the quality improves obviously.