A theoretical model characterizing a reported experiment on optical chaos synchronization switching is presented. Based on the model, the characteristics of optical chaos synchronization switching have been numerically simulated for different feedback strength and injection strength. The results show that: for a fixed feedback strength, both on-off switching ratio and width of the chaos switching will vary with the change of injection strength. When the injection strength equals to the feedback strength, the on-off switching ratio will reach a maximum. Furthermore, when the feedback strength and the injection strength are increased synchronously, both the on-off switching ratio and the width of the chaos switching will increase monotonicly.