The casting process of complex thin-wall aluminum alloy castings was described,and a double runner system with annular bottom injection was designed.The casting process was simulated by using ProCAST software,and temperature field of the filling and solidification process of the initial design was analyzed to determine the locations of shrinkage cavity and porosity of the casting.Through adding risers and cold iron in the appropriate locations to change the solidification sequence of the casting,the defect locations were effectively feeded and the casting production yield was improved.