Ag-Cu-Ti alloy can be used as active filler metal to achieve metal-diamond bonding, the effect of CNTs on the microstructure and properties of Ag-Cu-Ti filler metal was investigated. The results indicate that CNTs can improve the wetting spreading area of filler metal on the surface of steel substrate, and increase the melting temperature with ~9℃, and obviously increase the shear strength of brazed joint, when the content of CNTs is 0.2%, the maximum shear strength can be obtained with 49.3% amplitude. Moreover, SEM figures indicate that the addition of CNTs can refine the microstructure of filler metal, but excessive CNTs would coarsen the microstructure of Ag-Cu-Ti. For the fracture morphologies of Ag-Cu-Ti-xCNTs brazed joints, obvious ductile fracture mode can be observed on the fracture surface of Ag-Cu-Ti-xCNTs (x=0.05%, 0.1%, 0.2%, 0.5%) brazed joints. however, The fracture mechanism of Ag-Cu-Ti and Ag-Cu-Ti-1.0CNTs brazed joints shows obvious mixed fracture mode.