Abstract: In this paper, the functions and fundamental structure of atmospheric laser communication system are discussed The features and performances of laser sources and detectors-the core components of the system are presented Commonly, the laser communication systems with the functions of ATP are practiced by separating the signal beam and the beacon beam The characteristics of the available detectors-CCD, PSD, 4Q-PIN, 4Q-APD are analyzed The selecting rules are mainly the receiving FOV, sensitivity and position resolution.