A set of 6×, 10×, 16×, 25× and 40× magnifications of digital slit-lamp microscope optical system is designed with Zemax. The optical system structure of traditional stereo slit-lamp microscope is analyzed, on its basis, the digital slit-lamp is divided into shared front-objective, Galileo telescope and photographic lens, using parallel Galileo telescope system structure to change rate. The optical properties and the technical indicators of shared front-objective, Galileo telescope and photographic lens are discussed, and the appropriate type of the lens is selected. Under the good imaging quality foundation in coaxial situation, the optical system is carried out the transition to non-coaxial and optimized. The modulation transfer function curve values are mainly greater than 0.2 at the position of 115 lp/mm in 6×, 10×, 16×, 25× except the low diffraction limit at 40×, and the spot diagram shows that the spot size in different magnifications are substantially less than the Airy disk. The lens has a good imaging effect with simple structure, easy processing and low cost.