Optical detection of space target is the premise for debris collision avoidance, early warning and active removal, which is considered as the basis to safety protection of spacecraft and sustainable development of outer space activities. And lidar can achieve all-day detection and is an important supplement to passive optical payloads. This paper used detection system based on single photon detector, which had the time and position record function for the arrival signal, to measure the time-position three-dimension information of the target crossing the field-of-view of the detection system. And the twice Hough transforms were applied to determine the trajectory of the target at low SNR. The experiment results showed that the moved targets could be detected at the condition of SNR<2, and the trajectory could be determined accurately under the condition of bright background and target. This work hopes to provide reference for high sensitive detection of the dim fast target.