Abstract: The f- lens is an important essential component in laser scanning systems. For the shortcomings of current domestic laser scanning systems such as small working surface , slow measuring speed , low measurement accuracy, a large field of view(FOV) f- lens was designed with large relative aperture to improve the working efficiency. The designed lens is a negative distortion lens with the image space telecentric optical path. Expected parameters are as follows: 2=60，D=120 mm，f=500 mm. After calculation, the Zemax software was used to optimize the design for f- lens model. Finally ,a large-working-area large-relative-aperture f- lens was obtainde with an Airy disk diameter of 3.514m, a scanning range of 500 mm500 mm and an aperture of 6/25. The image is clear, the optimization results achieve the expected design target.