In the process of laser communication, laser guidance, rendezvous and docking in order to achieve the acquisition and tracking of long-distance targets, a laser tracking method based on single-element detector is proposed in this paper. A single-element detector is used to measure the distance information, and a fast mirror is used to scan the field of view in spiral line. With the angle information of fast mirror and distance information of detector, a three-dimensional image is generated. Through signal processing, the center of target in 3D image can be obtained and the control module drives the fast mirror to start next scan according to the difference between target center and FOV center, so that the target is always in the scanning FOV and target tracking is realized. The advantage of this method is that the single-element detector can be introduced into tracking task, and the array detector is no longer needed to locate the center of target, and therefore the echo energy density is much higher and the tracking range can be much longer, especailly with the incorporation of single photon avanche detector. With this method, the simulation experiment has been carried out and the target at 3.75 m is captured and tracked. The experimental results show that the simulation and experimental results are consistent with each other, and the acquisition probability of target with diagonal velocity of 9.07 mrad/s is 72.5%.