High precision and stable beam tracking is the premise of establishing free space laser communication link. An improved firefly algorithm is introduced to optimize the parameters of the proportional integral differential(PID) controller. At the same time, the model of the DC torque motor system is established. The optimized PID controller is applied to the system, and the experiment is carried out on the six dimensional simulation platform. The results show that for the same system, compared with the Ziegler and Nichols(Z-N) method, the optimal PID controller has better performance, the response speed, bandwidth and tracking accuracy of the improved firefly algorithm are improved by 40%, 33.3% and 25% respectively.