Abstract: The combination of aluminum alloy casting method and pouring riser system, subsidy, cold iron or chill sand is an effective measure to eliminate internal shrinkage hole and shrinkage porosity in complex parts of castings. By optimizing the differential pressure casting process of a large complex gearbox housing casting, chill sand was used instead of cold iron to adjust the temperature field of the complex parts of the casting to achieve simultaneous solidification of the parts. The subsidy was added at the hot spot of the casting, and the wedge-shaped feeding channel was artificially set to increase the effective feeding distance of the riser during solidification, and the problems of shrinkage hole and shrinkage porosity in the casting were solved.