With the advantages of non-contact and high accuracy, the machine vision detection technology is gradually replacing manual detection methods and becoming an important part of industrial production detection. As the front end, the optical system is a core part of the machine vision detection technology. A bi-telecentric optical imaging system was designed for the detection of smooth spherical surfaces within a radius of 10 mm. The optimized system was composed of 7 lenses and 1 filter, and 2 aspherical surfaces were used to correct the aberration. The modulation transfer function (MTF) curve was greater than 0.3 at 40 lp·mm^?1, which meaned that the system was of good imaging performance. Since the aperture was small and the object to be tested was a specular-like material, the lighting simulation was carried out, and multiple surface light sources were selected to illuminate the object. The simulation results show that the designed bi-telecentric optical system realizes the imaging of surfaces with large curvature, and a matching illumination method is proposed.