Abstract: Effect of mass fraction of Al-5Ti-0.2C refiner and refinement holding time on the microstructure and mechanical properties of 5356 aluminum alloy was studied by using optical microscope, scanning electron microscope, energy disperse spectroscopy and universal material testing machine. The results show that the grain of 5356 aluminum alloy was refined significantly after adding Al-5Ti-0.2C refiner. With the increase of refinement holding time and mass fraction of refiner, the grain size of aluminum alloy decreased first and then increased. The mechanical properties of aluminum alloy were improved after adding the refiner. When the mass fraction of refiner was 3% and refining for 20 min, the elongation of the aluminum alloy was the largest, which was 12.58%, and the aluminum has the best comprehensive mechanical properties.