As a relatively advanced detection method, lidar is widely used in the fields of unmanned driving, AGV, unmanned aerial vehicle, floor sweeping robot and so on. The mechanical scanning lidar is the core sensor of AGV and sweeper. In this paper, a lidar for robot is designed, which can scan the target 360 °. In order to reduce the overall size of the radar, the first coaxial structure is adopted. At the same time, the spherical cylindrical lens is used to compress the fast axis of the laser, and then the beam is collimated with the aspherical lens, so that the reflected light can obtain a small divergence angle. For the target with diffuse reflectance of 90%, the measurement distance is 60 m, and the half angle of laser emission of the emission system is ≤0.1 °.