In this study, the modification of Al-Cu alloy by adding grain refiner combined with different heat treatments (superheat treatment and thermal rate treatment) is investigated. The phase composition, solidification microstructure and mechanical properties of Al-Cu-Ti alloys are analyzed. Moreover, the melt structure transformation of Al-Cu-Ti alloys after different melt heat treatments was studied by DSC. The experimental results showed that the thermal rate treatment greatly refined the grain of Al-Cu-Ti alloy and improved the mechanical properties. Through the analysis of thermodynamic phase transition, it was found that the latent heat of fusion of Al-Cu-Ti alloy after superheat treatment and thermal rate treatment became smaller due to the increase of interfacial energy, which leads to refine the microstructure of alloy to some extent.