The brazing experiments of CBN abrasive grains and the steel with 0.45%C using Ag-Cu-Ti alloy reinforced by TiN particles as composite filler were carried out with heating temperature of 920 ℃ and dwell time of 5 min. The interfacial microstructure and characteristics among TiN particles, Ag-Cu-Ti alloy, CBN grains and the steel substrate were detected with three-dimensional video microscope, scanning electron microscope (SEM), energy dispersion spectrometer (EDS) and X-ray diffraction (XRD). The results show that the microstructure of Ag-Cu-Ti alloy is refined obviously by the well-dispersive TiN particles. The interfacial zone between the particles and the filler is uniformity and compact, and the microhardness of the filler layer is improved. Good combination between the filler and the substrate can still be obtained when the TiN particles are applied. The composite filler doesn’t take negative effects upon the chemical reaction between CBN grains and the filler. Good wetting ability of the composite filler is realized on the CBN grains during brazing, which ensure the hard join to the grains.