The pathogenesis of the small intestine, with several folds, is hidden. Generally, optical systems with a large depth of field (DOF) are conducive to obtaining abundant pathological information during diagnosis. However, current capsule endoscope optical systems that are available in the market have a small DOF. In this study, we propose a capsule endoscope optical system that can effectively produce images in the range of 7?100 mm DOF while ensuring a certain resolution. The field of view (FOV) angle of the proposed system is 100°. Additionally, its F-number is 5 and the modulation transfer function is greater than 0.35 (at 125 lp/mm frequency) in the full FOV, thereby meeting the imaging requirements of the matched OV9734 imaging chip. Furthermore, the tolerance analysis of this optical system shows that it can satisfy the requirements of conventional production and assembly within the machinability range.