A process of casting a complex aluminium alloy shell for high-voltage switches via 3D printing sand mold technology was introduced. Leveraging the advantages of 3D printing sand mold technology in design flexibility and rapid manufacturing, a targeted casting process design was conducted, including a gating system design, chill design, and sand mold (core) printing scheme. The optimized process design was verified via simulation technology, and the qualified products meeting the technical requirements of the high-voltage switch industry were finally obtained by casting preparation and inspection verification. Compared with the traditional mold scheme, the process will research the product. The whole production cycle is shortened by more than 50% without high-cost mold investment, which results in a rapid response, rapid preparation and rapid iteration of products, significantly improves development efficiency, and provides a convenient path for customized, differentiated and complex designs of castings.