In order to improve the strength of Cu/Al₂O₃ joint, vacuum brazing of copper to Al₂O₃ ceramic was performed using nano -Al₂O₃ strengthened AgCuTi composite filler (abbreviated as AgCuTi_p filler). The microstructure and mechanical performance of the brazed joint were investigated by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and shear strength test. Typical interfacial microstructure of Cu/AgCuTi_p/Al₂O₃ brazed joint is Cu/diffusion layer/Cu-based solid solution + Ag-based solid solution +Ti₂Cu +Ti₃(Cu, Al)₃O/Al₂O₃. The addition of nano-Al₂O₃ can improve the interfacial microstructure by inhibiting the growth of reaction layer near Al₂O₃ ceramic side, and promoting the formation of dispersed Ti₂Cu phase in brazing seam. Moreover, both thickness of diffusion layer and Ti₃(Cu, Al)₃O reaction layer thickened with an increasing holding time. Excessive dissolution of copper was occurred when holding time reached 20 min, which deteriorated the performance of the brazed joint. The highest shear strength of 82 MPa can be obtained when brazed at 880 °C for 10 min. The addition of nano-Al₂O₃ particles can refine the microstructure of brazing seam and decrease the mismatch of coefficient of thermal expansion between substrates and brazing seam. Therefore, the performance of brazed joint can be improved. The holding time can affect the microstructure and thickness of reaction layer, thereby affect the strength of brazed joints.