Abstract: Based on the superposition principle of welding residual stress and working stress,the heat efficiency of welding arc has been determined by measuring displacement of specimens under loading and unloading,and combining with calculation in the process of tensile experiment of welding specimen.Meanwhile,comparison of the heat efficiency obtained with measuring and calculation method was performed.The results show that welding heat efficiency obtained by two ways are almost the same,the welding heat efficiency can be obtained accurately,this paper has provided a new method of determining welding heat efficiency for welding heat process calculation.