Abstract: Based on EET theory,the effect of Zr content on solid solution strengthening of the brazing alloy was investigated. When the Zr content changed between 45%-12%,the max covalent electron number in the cell of Ti-Zr-15Cu-10Ni brazing alloy kept constant in the beginning,then decreased,and finally increased. However,when the Zr content was 37.5%,the effect of Zr element on the solid solution strengthening of Ti-based brazing alloy was apparent. Transient liquid phase diffusion welding of Ti₃Al-Nb alloy was conducted with Ti-37.5Zr-15Cu-10Ni alloy. When the joining temperature was lower than 1 000℃,the diffusion ability of brazing alloy was mostly influenced by the holding time. Under higher temperature,the diffusion ability of brazing alloy improved significantly,and the joining interface with homogeneous microstructure and no precipitation formed shortly in the isothermal stage.