The results have been achieved by adjusting the structure to improve the performance of micro injection molded isotactic polypropylene products. Annealing was adopted to optimize the performance of isotactic polypropylene micro injection molded gears. It was found that the annealing temperature shows greater influence on the crystalline structure of the micro injection molded gears than annealing time. The layer mechanical properties were greatly improved after annealing, about 1.7-fold for modulus and 1.9-fold for hardness of the micro injection molded gears relative to the unannealed sample. This is due to the fact the state of molecular chain aggregation tends to be consistent after high temperature annealing in the micro injection molded isotactic polypropylene gear sample.