The invention discloses a low pressure casting process for an aluminum alloy cylinder part. The aluminum alloy used by the method comprises the following materials in percentage by mass: 6.0 to 7.0 percent of Si, 0.3 to 0.5 percent of Mg, 0.1 to 0.2 percent of Ti, 0.05 to 0.15 percent of Fe and the balance of Al. After melting, thining, modification, and refining, the materials are subjected to low pressure casting and pouring; and after low pressure casting process of liquid lifting, filling, pressure maintaining and pressure releasing, the materials form a cast in a die cavity; and after a cast blank is subjected to solution treatment, and heat treatment of incomplete artificial aging, the cast has the advantages that: the texture is compact, casting defects such as pores, shrinkage porosity, shrinkage cavity, slag inclusion, and the like are avoided, the quality of the cast is improved; meanwhile, the working allowance of the cast is less, so the material utilization is improved and the production cost is reduced.