In this paper, the distribution and variation trend of temperature and velocity fields were obtained by numerical simulation of the casting process of shell die casting. According to the results of the numerical simulation, the die casting technology was optimized. The sound castings were produced. It was verified that shrinkage cavity and porosity could be reduced by increasing injected pressure and decreasing pouring and mould temperatures. The reliability of numerical simulation of die casting process was proved. In addition, the qualified products were obtained on the basis of the optimized die-casting parameters from the simulation results.