Abstract: The characteristics of PMF(pulsed magnetic field) force for grain refinement in solidification process was analyzed through mathematical analytic method. The main peculiarities of PMF force were shown as follows: It was found that the direction of PMF forces changes instantaneously in an individual impulse discharging period, and the PMF forces inside and outside the melt are in different directions in a certain period. In addition, the PMF force is attenuating in an individual impulse discharging period. All the three characteristics are the main reasons why the melt oscillates under PMF. Besides the characteristics as above, the PMF force has a stirring effect on melt in the medium-frequency PMF as used in this investigation. Futhermore, when the pulsed discharge frequency is equal to the natural frequency of solidification system, a resonance will happen to enhance the effect of pulsed magnetic force on solidification processing.