Abstract: After studying the specific property of the investment casting , the 3-D numerical simulation of temperature field based on the finite difference method (FDM) for the solidification process of investment casting has been developed by dealing mold/environment boundary and riser/ environment boundary condition with convection and radiation to improve old modeling. The numerical simulation of temperature field and shrinkage defect prediction for a valve casting, which was involved in 4 kinds of casting processes, were carried out. The good agreement has been obtained between the numerical simulation and the experimental result verification. Based on the numerical simulation result, the casting process of the valve for practical mass production has been set up.