Abstract: The effects of Al-5Ti-0.2C refiner mass fraction and refining holding time on the microstructure and mechanical properties of AlSi12 aluminum alloy were investigated by optical microscope, scanning electron microscope and universal material testing machine. The results show that the refining effect of adding Al-5Ti-0.2C to the molten aluminum for 2h has no obvious decline. Al-5Ti-0.2C refiner can obviously refine the grains of AlSi12 aluminum alloy. With the increase of refiner mass fraction, the grain size of the aluminum alloy decreases obviously. The elongation is improved,especially at high temperature. Through scanning electron microscope analysis, it is found that the fractures of the aluminum alloys added with the refiner are all ductile fractures, indicating that the AlSi12 aluminum alloy added with the Al-5Ti-0.2C refiner has strong toughness.