To reduce the number of detectors used in conventional binocular stereo cameras, while improving the measurement accuracy and compactness of the system, this paper proposes a design method for a binocular stereo vision optical system based on a single lens and a single sensor. First, based on the design principle of the traditional binocular optical system, to the best of our knowledge, a novel method of designing a framing lens array at the optical stop of the optical system is proposed to image two images on one detector simultaneously. Second, we propose a dual-frame lens array design method at the aperture stop position of the optical system that can image two images on one detector simultaneously. Then, the design principle of the method is analyzed theoretically, as well as a detailed analysis of the imaging position layout and the stray light elimination method of the dual-channel optical system. Finally, a single-lens binocular optical system with a focal length of 20 mm and a full field of view of 30° is designed using the method in this paper, and the analysis results demonstrate that the system has the advantages of good imaging quality and compact construction and provides a design idea for the design of a binocular stereo vision optical system.