The liquid crystal optical phased array, which has the ability of deflecting non-mechanical beam, can be applied to space laser communications acquisition-tracking system to realize fast, flexible, and multiple-user access. A fast-tracking method based on liquid crystal optical phased array is presented, and the method uses charge coupled device (CCD) as a beacon light detector. Proportional integral differentiation (PID) closed-loop control algorithm is used to generate beam angle of direction control point data. Agile deflection of the incident light beam can be achieved, which points to the center of the acquisition-tracking detector, thus the purpose of tracking is achieved. The theoretical simulation shows that PID closed-loop control system can suppress Gaussian white noise and the tracking accuracy is less than 6.5 μrad. Experimental results show that after around 10 ms adjustment, the system enters the state of steady tracking, and the tracking accuracy is less than 12.6 μrad.