A folding optical system which was aimed to shorten the axial length of the low‑light‑level night vision goggles was designed to improve the wearing comfort. Firstly， the overall design was given， which included the design of a foldable objective lens， a long working range， and dual channel eyepiece system. Next， the parameters of the objective lens and eyepieces were obtained through the theoretical calculation. Finally， an initial structure that met the requirements was selected， and the folding optical system was optimized by using the software. Compared to the traditional direct‑view night vision goggles， the axial length of the night vision goggles was reduced from 110 mm to 70 mm by using folding optical system， which was closer to wearer’s head and could effectively improve wearing comfort.