Abstract: Due to good heat preservation and poor air permeability of gypsum mould, it is difficult to avoid the shrinkage porosity defects of gypsum mould casting of complex thin-walled aluminum alloy. The formation causes of the shrinkage porosity were analyzed from the technological point, in which the liquid flow intersection and gating system have the greatest influence. By optimizing casting process, such as vent hole, inner gate setting, sprue and runner connection mode optimization, the formation conditions of shrinkage porosity are eliminated, so as to eliminate the shrinkage defects of castings.