Research on eye detection based on computer vision is very critical t o face recognition and gaze tracking. Furthermore, it is very important not only to related applications but also to the development of pattern recognition. Res earch findings on eye detection in recent 20 years are reviewed. Firstly, the existing classification methods are discussed and two new classification methods are proposed by recognition principle and detection results. Then, according to the detection results, the basic ideas, the advantages and the disadvantages of the eye detection methods are clarified. Meanwhile, the essence of all kinds of methods is tried to be revealed from different views and by different classification methods. Finally, the current situation of the eye detection research is analyzed and summarized, and the application prospect and development trend are discussed.