Abstract: In this paper,the control technique of optical chaos,also called the period windows technique, with the relative technique of searching and locating of the period windows is presented explicitly to solve the usual difficulty of looking for the period windows in experiment.The period windows controlling technique can be easily used in optical system for chaos control,especially in the higher output,low input system without any accessory device to get the non chaos output.In computer imitation experiment of the chaos control of optical second harmonic output,the strong period second harmonic output obtained.This fact shows that this technique is much better than usual method.