Aiming at the difficulty of the coarse tracking control technology of free space optical communication system, a cascade coarse tracking control structure is designed. A linear auto disturbance rejection controller is introduced, and the linear extended state observer is used to observe the total disturbance of the system. The simulated dynamic tracking experiment is carried out to compare the control errors of the linear auto disturbance rejection controller and the proportional integral differential controller under the disturbances of 0.5 Hz, 1 Hz and 2 Hz. The experimental results show that the linear auto disturbance rejection controller has higher control precision and better stability.