Induction heating is widely used in the workpiece heat treatment because of its characteristic such as being flexible in control, high in thermal efficiency and no pollution in environment and so on. Aimed at being difficult to start under heavy load, the paper explored the starting strategy of electromagnetic induction heating medium frequency power supply. In the paper, it made anatomy of the reasons on being difficult to start for the current type of induction heating power supply, studied on the constraint relation among the starting control parameters, discussed the selection principle of the rectifier trigger angle and so on, and finally, gave the conditions for successful startup control. Based on MATLAB simulation software, the simulation results verified the correctness of the proposed strategy. The experimental results show that the proposed method is feasible and reasonable.