Binocular stereo vision is an important measurement method widely used in the field of machine vision, which has the advantages of high precision, simple structure, high measurement efficiency and non-contact. The main task of binocular stereo vision is to get two images of the same scene by two cameras in different positions, then get the initial disparity map via stereo matching, and finally optimize the previous disparity map. Starting from the background and research significance of stereo matching technology, this paper first introduces the basic principle of binocular stereo vision, then explains the four steps of stereo matching. And finally reviews the research status and existing problems of passive stereo matching algorithms.