Abstract: Objective The aim is to explore the influence of heat input on the equivalent residual stress during the welding process of Ti-6Al-4V titanium alloy by tungsten inert gas arc welding (TIG). Methods 3 mm thick Ti-6Al-4V titanium alloy is selected as the research object to conduct simulation and modeling of the welding process and predict the equivalent residual stress distribution of the model under different parameters. Results The results show that the post-weld equivalent residual stress of the 3 mm thick Ti-6Al-4V model is correlated with the welding heat input. The maximum transverse equivalent residual stress of the model is located in the weld area and near the weld area, and gradually decreases along both sides. Longitudinal equivalent residual stress shows “mountain” distribution with large middle and small ends. A slice view of the weld of the resulting model under different parameters is selected, which indicates that the transverse stress is concentrated in the middle and at both ends. At the same time, special abnormal spots can be found in the section analysis of some welding parameters, which are similar to a welding defect caused by excessive welding heat input. Conclusion By selecting the double ellipsoid model as the heat source and realizing the filling of the weld area by adding the life and death units, the numerical prediction accuracy of the equivalent residual stress reaches more than 85%, which can provide an effective idea for the actual welding optimization.