The technology of computer numerical simulation on casting process is an important frontal field of material science and technology. The numerical simulations of camera shell in the pressure die casting process were carried out. The distributions of temperature and solidification time in the filling process were obtained. Based on the simulated results and the Niyama criterion G/ R , the positions of slack were predicted, which were agreement with the practical result. Consequently, an improved scheme was presented, in which the workpiece defects were obviously reduced. So it’s significant for the application of numerical simulation on improving the quality of the casting, shortening the period of producing, reducing the cost and guiding the engineer for taking reasonable method to optimize the technological design.