The optical fibre endoscope with cold light is still mainstream in the endoscope market, but the inherent structural characteristics of the optical fibre endoscope lead to its shortcomings, such as high price, inconvenient to carry, and easy distortion of image. The micro medical electronic endoscope can receive the front-end optical system image through the miniature CCD (Charge Coupled Device) and transmit the image to the display through the cable, which greatly solves the limitations of the optical fibre endoscope. In this paper, using ZEMAX software, an optical imaging system with 75∘ field of view is designed. The system consists of four lenses, and all of them are standard spherical lenses. The maximum aperture is 2.2 mm and can match the 1/10-inch CCD. The distortion of the edge field of view is less than 20%, the aberration is small, and the light convergence is good. The maximum spatial resolution is 175 lp/mm.