Abstract: A TiB₂/Cu-Zr composite was fabricated by an in-situ reaction synthesis method, and the microstructure was studied. The results showed that TiB₂ particles exist in two patterns and its distribution is homogeneous with its size of 0.5 μm~10 μm. A reaction model of TiB₂ in molten metal is established combined with the thermodynamics of TiB₂ particles in solid and liquid matrix. Finally, the growth mechanism of two kinds of TiB₂ particles is proposed.