Abstract: The formation Of brittle intermetallic compounds at the interfaces of diffusion bonds is the main cause which lead to produce poor bond properties. Therefore, it is very important to research on and establish the formation and growing model Of intermetallic compounds at the interfaces for the control process of diffusion bonding.In this paper, according to the diffusion dynamics and the thermodynamics, the formation principle of interface intermetallic compounds for the multi-composition diffusion couple, the flux-energy principle, was put forward. In the light of diffusion theory, the formation capacity of the phase at the interfaces is determined by specific properties of the composition in the diffusion couple and the composition proportion of the formed phase is in agreement with the atom diffusion flux. In accordance with the flux-energy principle, the microstructure of the Ni/Ti interface is Ni/TiNi₃/TiNi/Ti₂/Ni/Ti.On the basis of this paper theory, multi intermetallic compounds with the equivalent flux-energy can be formed at the interfaces at the same time.