Abstract: Arthroscope is a kind of optical device which can observe the internal structure of our joints, as an endoscope to make a diagnosis and give treatment to the joint. The gradient refractive index(GRIN) lens has many merits such as light weight,small volume and good image quality, according to which a optical system with simple structure was designed with Zemax for-1/10＂CCD arthroscope. The system has 60 field of view and the F number is 6, the working distance is ~5mm. The value of modulation transfer function (MTF) is more than 0.2 at 125 lp/mm, the resolution of the system is up to 4 m, the spot diagrams of all configurations are smaller than Airy disk. The total track is 204mm, the biggest caliber is less than 4.6mm. According to the characteristics of arthroscope,the system meets the requirement.