Abstract: By introducing Ti alloy interlayer between (Ti+B₄C) reactant and Ti alloy substrate, the effect of thickness variations of Ti alloy interlayer on the microstructure and mechanical properties of the interface of TiB₂ based ceramic/Ti-6Al-4V graded composites has been discussed, which were prepared by reaction bonding in high gravity field. The thermodynamic calculation shows that the adiabatic temperature of synthesis reaction is much higher than the melting point of Ti alloy, which ensures Ti alloy interlayer with different thickness completely melts. The XRD, FESEM and EDS analysis results show that the graded interface zone between ceramic and Ti alloy substrate forms, and the thickness of which increases with increasing thickness of Ti alloy interlayer. The volume fraction of TiB₂ phase and TiC_1-x gradually reduces, but the volume fraction of TiB first increases and then decreases from ceramic matrix to Ti alloy substrate, finally, on which there is the presence of the graded composite structures characterized by the size and distribution of TiB₂, TiC_1-x and TiB ceramic phases. And hardness distribution trend of the gradient connection area becomes smooth and shear strength improves gradually.