In order to investigate the changes in the optical disk properties with injection shot number, the physical properties, such as weight, thickness and birefringence were examined. Overall, the weight and thickness changes resulted in similar trend, while the birefringence showed a slightly different trend. The thickness and weight remained constant up to 700 shots, and slightly increased and reached plateau around 1,100 shots, For the birefringence, its value showed gradual increase at initial stage and reached constant value after 300 shots. To resolve such difference in trend, the injection molding cycle time, the filling time and the injection peak preassure were examined. In addition, the birefringence of disk along the radius was measured. It was observed that the birefringence decreased with increasing of radius. The possible origin of birefringence variation in injection molding of optical disk was discussed.