Abstract: Dissimilar alloys of TC4 titanium alloy and LF6 aluminum alloy were butt joined successfully by TIG arc and AlSi12 filler metals.Temperature distribution and relationship were investigated by finite element method(FEM) numerical simulation and experimental validation.The microstructure of the interfacial layers was measured by scanning electron microscopy(SEM).The results indicate that the temperature distribution of Ti/Al arc welding-brazing joint is extremely asymmetrical, the titanium side exhibits high temperature gradient and narrow high-temperature zone, while the aluminum side exhibits low temperature gradient and wide high-temperature zone.The high-temperature zone trends to assemble near the titanium side in cooling stage.The interface roughly parallel to the isotherm of the temperature field as the electrode point at titanium root face.This leads to a symmetrical temperature distribution at brazing interface and seam near titanium side, which can improve interfacial reaction nonhomogeneity.It is the key factor to form brazing interface with symmetrical microstructure and welding-brazing joint with high performance.The water cooling technology can accelerate the cooling process, cutting down the dissolution of titanium and retard the growth of intermetallic compounds.The interfacial reaction layer morphology is cellular rather than serrated shape in air cooling condition.