An advanced measurement method based on the binary fringe patterns defocusing is proposed to measure the three dimensional(3D)shape of the mirror.The geometrical optics principle of mirror reflection is studied and analyzed,and according to the optical characteristics of the mirror,a liquid crystal display(LCD)screen displaying binary fringe patterns and a camera observing the fringe patterns reflected via the tested mirror in the process of experiment.Binary fringe patterns defocusing projection is preferred instead of traditional sinusoidal fringe patterns in order to overcome the problem of image fuzzy at the surface of under test mirror.