Abstract: The filling and solidification processes of the primary coolant 90° bent pipes in pressurized water reactors(PWR) were simulated by ProCAST software.The simulation results show that molten steel can be filled smoothly,which demonstrates that the gating system plan meets the directional solidification principle.The locations of shrinkage and porosity in the bent pipes were predicted by using the solid fraction method.A series of technique optimizations were carried out in order to eliminate the shrinkage and porosity,so an optimized casting technique was finally obtained for the bend pipes.It is indicated that the casting yield of the bent pipes can be increased using ProCAST software analysis.