Abstract: As a low-cost and high-efficiency welding method, arc overlaying welding has a broad application prospect in the field of material surface repair. In this study, ultrasonic energy is introduced into the TIG overlaying process to improve the welding quality of aluminum alloy by coupling the ultrasonic frequency pulse electrical signal with the low-frequency AC TIG welding electrical signal. The weld formation, microstructure, and hardness of overlaying welded joints of 5083 aluminum alloy were compared before and after implementing an ultrasonic pulse electrical signal. The results show that the weld formation changes towards the trend of decreased fusion wide and increased surplus height with the increase of the output voltage of the ultrasonic power. The grain size changs to some extent, but the grain morphology changs little after implementing the ultrasonic treatment. Grain refinement is the most significant in the fusion zone, but it is not obvious in the weld zone and the heat-affected zone. On the contrary, grain coarsening is obvious with the increase of the output voltage of the ultrasonic power. The distribution of the second phase in the fusion zone and the heat-affected zone shows an aggregation phenomenon. The ultrasonic effect has a great influence on the distribution of Mg element inside the grain. The segregation degree of Mg element at the grain boundary could be weakened by increasing the output voltage of the ultrasonic power. The hardness test results show that the weld hardness increases after coupling the ultrasonic frequency pulse electrical signal.