Abstract: Numerical simulation on welded joint of 45 steel using electromagnetic heating was made by ANSYS. The temperature and residual stress field were analysed. The result showed that the crack tip in the welded joint melted and dulled after discharge, the stress concentration also was reduced, in addition, the three residual compressive stress field around welded crack tip was appeared. The tensile properities were tested to compare the mechanical performance before and after pulsed current discharges. The result indicated that tensile strength and elongation were improved. Numerical analysis and experimental research confirmed the feasibility of applying electromagnetic heat strengthening technology into welding field.