In order to meet the actual needs of minimally invasive medical surgery, the Zemax software was used to design a medical endoscope for the treatment of urinary system diseases, which could not only solved the problem of the excessive diameter of traditional ureteroscopes, but also retained the high resolution of the visual system. The light wedge was used to convert the light, and passed through the fiber transmission beam in a rigid endoscope. The final designed endoscope system has an F number of 4.5, a system object field of view of 80°, a viewing angle of 6°, a circle diameter of fiber transmission beam of 0.85 mm, an optical lens diameter of less than 1mm, a working distance of 6 mm, and a working length of 430 mm. The modulation transfer function (MTF) is greater than 0.2 at 120 lp/mm, and the imaging quality meets the visual requirement.