Abstract: The error factor of injection molding has a direct effect on the quality of a plastic freeform optics. In the process of injection molding, the combination of injection parameters and the injection process control significantly affects the error of molded plastics. In order to obtain higher precision plastic optical components, this paper focused on some key parameters such as the temperature of mold and injected material, injection pressure, holding pressure and holding time, and analyzed their effect on the quality of injected part. The theoretical research was proved by the experiments. The result indicates that, the shrinkage rate of volume is reduced, and the form and surface accuracy is improved by increasing the temperature of injection and mold, the pressure of injection and holding pressure. Thus, the precision plastic optical components can be obtained with the error of less than 0.1μm.