Abstract: In this paper, the microstructure and the precipitations in the interface were studied for the honeycomb sandwich construction in titanium alloy. The valence electron structure of the brazing joint interface was calculated by the empirical electron theory(EET) in solid and molecules. The inter-atomic binding force was analyzed and the relationship between it and the microstructure was discussed. The TiN i3(Cu, Zr)-compound with hcp lattice structure and the Ti(Ni, Zr, Cu) solid solution with bcc structure were formed in the welding. The maximum valence electron and maximum crystal electron for the matrix was0.305 9 and 1.397 3, which represented the ability of the strength and ductility for the crystal respectively. For the TiN i3(Cu, Zr) compound and the Ti(Ni, Zr, Cu) phase, the maximum valence electron was 0.055 8 and 0.303 7 respectively, and the maximum crystal electron was 0.993 5 and 1.392 8 respectively. Thus, the ability of the strength and ductility for the Ti(Ni, Zr, Cu) phase and the matrix is better than that of the TiNi₃(Cu, Zr)-compound. The discontinuity of the microstructure in the interface is disadvantage for the strength and ductility.