Arc additive manufacturing technology with high efficiency, low cost, short manufacturing cycle, and no molds represents a new method for the production of large and complex metal structures. In this study, based on the ANSYS parametric design language APDL, the thermophysical parameters of ER50-6 carbon steel-welding wire are obtained using Jmatpro and the dynamic simulation of arc additive manufacturing process is realized by the birth-death-element method. The feasibility and correctness of the simulation of the temperature variation in welding and post-weld cooling are verified via comparison with the experimental results. The variation rule of the temperature field in arc-additive manufacturing under different substrate thicknesses is analyzed to obtain optimal substrate thickness. Furthermore, the study explores the variation of the temperature field during the multi-layer additive manufacturing process of straight, single wall parts. This provides an important theoretical basis for forging modification process of the formed parts based on additive manufacturing residual temperature.