Abstract: In this paper, 3D printing pattern is combined with plaster precision casting to improve the casting quality of impeller parts. The molding position and wax dipping process of the pattern were analyzed. The high quality impeller pattern was prepared with selective laser sintering (SLS). Based on the excellent sequential solidification and exhaust, a top-pouring gating system was designed, and the design scheme was simulated with ProCAST software to verify the rationality. Then, qualified castings were successfully obtained with vacuum pressure pouring, and the influence of T5 heat treatment on the mechanical properties of castings was studied. The results show that SLS can combine well with plaster precision casting. The mechanical properties of 3D printing patterns depend on whether the stress surface is the printing surface. Wax dipping process can significantly improve the mechanical properties of the patterns. After T5 heat treatment, the tensile strength and Brinell hardness of the casting increase from 184 MPa and 57 HB to 330 MPa and 109 HB, respectively. The melting and passivation of eutectic Si are the main factors for the improvement of mechanical properties.