The TiB 2/Al 4.5Cu composite was fabricated by K 2TiF 6/KBF 4 mixed salts reaction in Al 4.5Cu molten metal. The solidification microstructure and mechanical properties of the composite was researched by SEM, XRD and MTS etc. The reinforced TiB 2 particle less than 2 μm, with nearly spheroidal form was uniformly distributed in the matrix, reinforcing and refining metal matrix. Moreover, the TiB 2 particle was combined with AlCu4 alloy well. When the K 5TiF 6 and KBF 4 mixed salts addition is 20% of the metal matrix, the mechanical properties of the composite is best, UTS is 352 MPa, EL is 4.4% , HB is 146.