Abstract: An experiment of the solidification process of steel billets under linear electromagnetic stirring (EMS) was carried out on a special setup of which a unilateral water cooling copper plate was mounted to the mould. A computer dynamic data acquisition system was provided to perform real-time measurements of some heat exchange parameters during the solidification of steel. The results show that in the mould the heat flux increases obviously in initial solidification period under the action of EMS to expedite the overheat dissipation in molten steel. Thus, the internal temperature of the ingots tends to be distributed uniformly with the temperature gradient at the solidifying front reduced. As a result, the growth of columnar grain is suppressed, which will be helpful to the nucleation in molten steel and the formation of equiaxed grain solidification structure. Therefore, the rate of equiaxed grains in ingots with EMS can be improved to 76% from 47% without EMS. The fact indicates that the overheat dissipation in molten steel with EMS is one of key factors to increase the rate of equiaxed grains in the solidification structure.