Squeeze casting is one of the modern casting processes, which was invented to address these shortcomings and has a high potential to produce sound casting alloys. Magnesium Alloys are the lightest structural alloys commercially available and have great potential for applications in aerospace and automobile industries. In this article, the influence of pressure variation on the microstructure and defects formation in the Al-7%Mg alloy during squeeze casting process was studied. It was observed that a small external pressure of 20 MPa promoted structural refinement and a significant increasing in the ultimate tensile strength. This improvement in structure and properties is attributed to increasing in the cooling rate during squeezing.