A beam scanning system is a fundamental component of a light detection and ranging (lidar) system, as it determines the field of view (FOV). To increase the FOV and maintain a specific angular resolution, multiple laser diodes are often used in a mobile lidar. However, the time response of different laser diodes is different, resulting in a mutual ranging difference between different ranging channels of the lidar. Risley prisms are outstanding beam pointing devices that offer good prospects for beam scanning of mobile lidars because of their notable features such as large FOVs and high pointing precision. In this study, the optical and mechanical configurations of a scanning system are designed based on the beam-pointing and scan-pattern models, which can realize two-dimensional scanning over a wide FOV. The horizontal and vertical FOVs of the scanning system are 360° and 30.4°, respectively. When the scanning system operates at a frequency of 5 Hz and scan lines of 30 with a 1-MHz repetition rate laser, the horizontal and vertical resolutions are 0.05° and 1.0°, respectively. These performance indicators are comparable with those of mainstream mobile lidars and can meet the actual requirements of mobile lidars. Most importantly, this scanning system can eliminate ranging differences between different channels, and significantly improve the ranging precision of the lidar.