In order to solve the problems of coarse grain and poor mechanical properties of wire arc additive manufacturing specimens, mechanical vibration was applied in the process of wire arc additive for manufacturing 2319 aluminum alloy, and the effects of mechanical vibration frequency and amplitude on the microstructure and mechanical properties of specimens were analyzed. The results show that the mechanical vibration improves the fluidity of the molten pool, making it more spread out, while the layer width increases and the layer height decreases. Vibration breaks the dendrites during the growth process, which refines the INZ grains by 1449 μm and the ITZ grains by 468 μm. The content of solute elements at dendrites gap decreases, so that the precipitated phase becomes intermittent and fine, so that the intervals of PLC phenomenon increases, which significantly improves the elongation of the material. The longitudinal and transverse elongation increase by 382%, 157% and 293%, 525%, respectively, when the mechanical vibration frequency and mechanical vibration amplitude change, while the strength of specimen does not change significantly. It is found that the use of mechanical vibration-assisted arc additive manufacturing can significantly improve the plasticity of the specimen without affecting the strength, which provides theoretical basis and technical reference for its wide application.