In order to meet the demand of gun sight in military products，a set of gun sight which can realize 8× ~32× continuous magnification is designed. The design idea and method of the gun scopes are described in detail. Firstly， according to the design index，the objective lens group，eyepiece group and relay mirror group are decomposed and calculated. Then，the Gauss optical design of the objective lens，the eyepiece and the whole gun aiming system is carried out to determine the complexity of the whole system and the optical structure parameters. Then，according to the results of Gauss structure design，the initial structure is selected，and the optimization operand is selected according to the design index to optimize the system. Finally，the evaluation of the overall system design and optimization results is completed. In the final design results，the objective lens of the gun sight has an aperture of 56 mm，the eyepiece has an aperture of 50 mm，and the total length of the system is 410 mm；the aberration of the low magnification group is 2.4%，the on-axis diffuse spot radius of the high magnification group is 6.2 μm，the off-axis diffuse spot radius is 8.3 μm，and the aberration index meets the design requirements.