Abstract: Minimally invasive endoscopic surgery offers the advantages of smaller incisions and faster postoperative recovery, addressing the limitations of narrow field of view and short working distance encountered by surgeons during endoscopic thyroid surgery, the design of an endoscopic optical system featuring a Z-shaped optical path with a wide field of view and extended working distance was presented. A total internal reflection (TIR) 30° viewing prism fabricated from high-refractive-index glass was employed to achieve a full field of view (FOV) of 110°. This design effectively addressed the issue of peripheral field-of-view vignetting commonly observed in conventional viewing prisms that rely on reflective coatings.The Z-shaped optical path was realized through the integration of two 45° right-angle reflecting prisms and a rod lens system. The proposed endoscopic optical system was designed with a working distance of 50 mm, an angular resolution of 3.22 C/(°), an optical aperture of 3.8 mm, working length of 340 mm, and a total system length of 660 mm. The design meets practical application requirements, delivering excellent imaging performance and manufacturability. This work provides valuable engineering insights and practical significance for the enhancement and adaptation of endoscopic systems across various clinical scenarios.