Abstract: On the basis of adding 0.1wt% Ce, the effect of the Al-5Ti-1B refiner content (0wt%-0.4wt%) on the microstructure and tensile properties of A356 cast aluminum alloy was comparatively studied. The results show that with increasing content of Al-5Ti-1B refiner, the average secondary dendrite spacing of α-Al dendrite decreased first and then increased, and reached the smallest value of 37.3 μm when the content of refiner was 0.2wt%. The proper amount of refiner promoted the eutectic silicon shape changing from long and narrow fibrous to thick and short rods, and resulted in the reduction of equivalent diameter and aspect ratio of eutectic silicon; but the excessive amount of refiner caused the sharpening of eutectic silicon. After adding the refiner, the tensile strength and percentage elongation after fracture of the aluminum alloy all increased, and increased first and then decreased with increasing refiner content. The comprehensive modification effect of the aluminum alloy after adding 0.2wt% refiner was the best, and the tensile properties were the best; the tensile strength and percentage elongation after fracture increased by 20.7% and 66.7% compared with those without adding refiner, respectively.