To improve the fringe projection efficiency and measurement accuracy of the optical 3D measurement system, a binary defocusing method is proposed to rapidly project the coded fringes and the binocular stereo matching algorithm is used to obtain the parallax information. First, the Bayer dithering technology is used to convert the projected grayscale fringes into binary fringes to reduce the effect of the projector′s defocusing on the contrast and depth of field drop. Then, the wrapped phase is expanded into absolute phase by means of multifrequency heterodyne method, disparity constraint relation and average error sum of squares cost calculation are used to obtain the best phase matching point. Finally, the depth information and threedimensional information of the measured object are obtained through the principle of triangulation and dualtarget positioning. Through experiments on precision balls and statues, it is proved that the measurement accuracy of the method proposed in this paper is close to that of the traditional twelve-step phase shift measurement, and is 52.8% higher than the traditional three-step phase shift.