Abstract: Based on the assignment test,the thermoelec-tric equation was obtained by least squares theory.Through designing the insulation clamping and the temperature offset of dy-namic error,the actual thermal cycle curve was obtained in heat-affected zone of laser welding.By high-temperature plasma being simplified as a dot heat resource and heat resource being linear for welding of thin plate,the mathematical model of laser welding for high strength steel was established and analyzed based on the principle of superposition,and the theoretical thermal cycling curve of welded seam in heat-affected zone was achieved.The comparison between the actual thermal cycling curve and theoret-ical thermal cycling curve and that between the actual weld width and the theoretical weld width indicated that the dot heat re-source and linear heat resource model can explain the thermal cycle process of laser welding for high-strength steel.