Al-Si alloy was melted by using vacuum induction melting furnace heated with medium-frequency induction and stirred simultaneously under Lorentz force. The experimental results were discussed with respect to the theoretical analysis of the Lorentz force on the molten alloy. It was found that Si phase tends to homogenize and aggregate along the direction of axis in the alloy under the effect of Lorentz force. With increasing stirring duration, Rod-shaped Si phase has a tendency to break and passivate on the edge. Vickers hardness measurement indicated that the microhardness of Al-Si alloy was improved after electromagnetic stirring. This result can be mainly attributed to the improvement in spheroidization of Si phase and aluminum phase.