Abstract: Structured light-assisted stereo vision technology can solve the problem of the measured object with sparse characteristics, so as to realize the high precision measurement of the geometric dimension of the object.The method of using the polar line and the fringe order double constraint was proposed, which was based on the principle of polar constraint in binocular camera and fringe order in multi-frequency heterodyne. Using this method, the stereo matching area was reduced. And during the stereo matching process, a weighted image template was used, the initial matching point was determined by using the phase information and the similarity template matching method, and the sub-pixel matching was realized by the two-dimensional curve fitting method according to the spatial distance and the phase difference of the initial matching point and the polar line. Experiments show that the method is applied well in small field of view measurement, and can achieve fast and accurate measurement for spheres with a diameter of 10 mm.