The way of pulse discharge strengthening is introduced, and the electromagnetic heat pulse discharge method can increase the strength and toughness of welded joints. 16Mn low alloy steel welded joints are used in the ZL-2 super pulse current generator, and the test of pulse discharge strengthening is carried out. And the mechanical performance comparison test of welded joint is finished. On the universal tensile machine, tensile strength test before and after strengthening has been done. On the S-4800 scanning electron microscope, micro-fracture morphology is analyzed. The results show that electromagnetic heat strengthening test is carried out based on the appropriate discharge parameters. In the junction of weld and base metal near the heat affected zone of the fracture, there is a white layer organization. It appears to improve the mechanical performance of welded joint, and enhance strength and toughness of welded joints.