Microstructure and macro-micro mechanical properties of the joints of Ti-xZr-15Cu-10Ni brazing fillers (mass fraction x = 10, 18, 37.5) were studied by in-situ tensile test, SEM, EBSD and EDX. It was found that although the increase in the Zr level lowers the melting point of the brazing materials, which is beneficial to reduce the time of manufacturing and the wear of the equipment, the brazing joints became harder due to solid solution hardening and transformed from a ductile to brittle fracture mode. The microstructural analysis revealed that the increase of Zr level increases the grain size, which leads to high strain gradient across the brazing joints. Thus, high Zr in the brazing joints reduces the ductility of the joints. In this study 10% Zr is found to be the most compatible one with the Ti-6Al-4V matrix. However, in practice, 18Zr is the optimal brazing material for engineering applications due to the balance of the mechanical performance, cost, reliability and applicability.