The cast Al-Si alloy was fabricated using the Additive Pressure Casting (APC) method. The effects of holding pressure from 50 to 400 kPa on the density, cooling rate, and mechanical properties of the alloy, and the corresponding mechanism were discussed. The results indicate that the application of high holding pressure (300 kPa) enhances the feeding ability of the alloy, leading to an increase of the density. Meanwhile, the cooling rate of the alloy is increased by 100％. In addition, the tensile testing results show that the increase of holding pressure from 50 to 300 kPa improves the tensile strength and elongation of the alloy by 6.2％ and 81.3％, respectively. However, excessive holding pressure (400 kPa) might lower the density and cooling rate of the alloy due to the feeding channels being blocked.