Abstract: The research progress on metallurgical defects and their mitigation through heat treatment in wire arc additive manufacturing(WAAM) of Ti-6Al-4V(TC4) titanium alloy was reviewed. It provided an in-depth analysis of the typical metallurgical defects in WAAM-TC4, including microstructural heterogeneity, porosity, crack propagation, and residual stress, along with their detrimental effects on material properties. The latest advancements in heat treatment regulation, both domestic and international, were critically evaluated. Furthermore, the influence patterns of different heat treatment processes on performance were compared, which could provide a theoretical basis and experimental guidance for selecting heat treatment process in practical production. The review offered valuable insights for a deeper understanding of the heat treatment regulation mechanisms in WAAM-TC4 and for optimizing its material properties.