Abstract: The effect of low pressure die casting holding pressure on the microstructure and mechanical properties of AlSi7Mg aluminum alloy was studied. The results show that the samples prepared with high holding pressure（320 kPa）have dense microstructure and excellent mechanical properties. Compared with the alloy with a low holding pressure of 90k Pa, when the holding pressure reaches 320 kPa, the secondary dendrite arm spacing of the alloy with a cooling rate of 1.5℃/s and 5 ℃/s decreases by 24.2% and 8.6%, respectively, the diameter of eutectic silicon decreases by 4.7% and 9.7%,respectively; the length-width ratio of eutectic silicon are decreased by 4.8% and 6.0%, respectively. The high holding pressure makes the casting process have good filling performance and fast cooling rate, thereby improving the mechanical properties of the AlSi7Mg alloy.