Using analysis methods of stretching test，SEM，EDS and microhardness test to investigate and research the mechanical properties, the fracture mechanism，the reacting phases are produced and the distribution range of vacuum diffusion bonding joints of Ti-6Al-4V/Cu/304. The results show that when bonding pressure is 5.0 MPa, the tensile strenght of the joint increases at first, but decreases with the increasing of bonding temperature and time, When bonding temperature is 1223K, bonding time is 3.6ks, there is a maximum tensile strength that is 163 Mpa. However, it will be disadvantageous to the performance of the joints, when bonding temperature and time extended overly. Using Copper foil as the interlayer, the intermetallic compounds did not generate in interface of Cu/304，Therefore, it formed multi-phase transition organizations by solid solution, intermetallic compounds in interface of Titanium alloy/Cu，such as TixCuy, TixFey and so on. The effect of TixCuy on strength of the joints is slightly larger than TixFey compound. The fracture mainly happened in the titanium alloy side Ti2Cu intermetallic compound in region Ⅱfor the source dehiscence, developping inⅡ-Ⅲ area junction weak intermetallic compounds of diffusion layer. It is brittle fracture. Therefore, it is the main way to improve the joint strength by improving the interface structure of titanium alloy/Cu side.