With the Taguchi method, the process parameters of dynamic injection molding are optimized and the relationship between processing conditions and the physical properties of isotactic polypropylene is explored. The results show that vibration frequency and vibration amplitude have greater influences on mechanical properties of isotactic polypropylene than injection velocity and packing pressure in most of our experiments. The samples' impact strength could be improved by about 40% with optimum parameters. The morphology and crystallinity are also explored with DSC and WAXD.