With TIG arc as heat source and AlSi5 wire as filling mental, the dissimilar material joint fabricated by TIG arc welding-brazing process between Ti-6Al-4V (TC4) and AlMg6 was studied with SEM, EDS and XRD. The temperature field and fracture behavior of the joint was investigated. The results show that aluminum side of the weld joint reveals a typical property of wire fed TIG welding, while Ti side which is base metal shows a property of brazing welding. Thickness of the weld interface increases with higher peak temperature and the interface microstructure becomes more complicated. Reducing high-temperature residence time can cut down the thickness of the interface, but with the peak temperature increasing, big cooling speed produces high stress in the joint, thus forming cracks through the grain boundary. In Ti/Al brazing weld joint, cracks which grow from gas cavity and micro-cracks in Al side are a typical hybrid composed of ductile and brittle fracture. Besides, over melting and dissolving of the Ti base metal will enlarge the size of the gas cavity, so the quantity of the heat input and melting of the base metal must be strictly controlled.