Location and tracking the human faces is one of the critical technologies in free stereoscopic display system.But because of illumination variation and some other reasons,it is difficult to detect human faces accurately and fast.In this paper,an infrared face detection based on real Adaboost algorithm and Cascade structure is implemented.With active infrared illumination and separating of visible light,the problem caused by variation of illumination is almost solved.Meanwhile,the combination of real Adaboost and Cascade structure pays more attention to the human faces which is more difficult to identify,making the detection more robust and quicker a lot.In the detection of video sequence,all human faces can be detected,and misdetection rarely appears.The average processing time on a windows XP,PIV 2．4 GHz PC is about 40 ms for a 640×480-pixel image．So the improved detection is real-time.In addition,experiment proves that the improved detection is robust when there is variation of facial expression or a little degree leaning of human face.