Abstract: With development of vehicle-borne opto-electronic system, the sight with multi-functions has become a trend. This paper presents common path design for TV sight/visual sight. For visual direct-view sight, magnification, field of view, exit pupil diameter and eye relief are 8^×, 5°, φ4 mm and not less than 15 mm respectively, while F number and focal length are 6 and 110 mm respectively for TV sight. Then tolerence of the results is analyzed. Finally, strict tolerance of parts fabrication and system assembly are formulated according to the analysis of tolerance. For 2.3 m×2.3 m target, identification distance is more than 4 km, which can meet imaging demands.