The invention discloses a synchronous positioning and composition algorithm based on point cloud segmentation matching closed-loop correction, and belongs to the technical field of robot autonomous navigation and computer graphics. According to the algorithm, inter-frame matching is carried out on feature points extracted from three-dimensional point cloud to obtain relative pose transformation ofthe robot, meanwhile, the obtained pose is stored at the rear end in a graph form, and then the point cloud is recorded based on the pose to form a map; the point cloud is fragemented and stored by using a point cloud segmentation and description algorithm, and the point cloud fragments are matched by using a random forest algorithm to form a closed-loop constraint condition; and finally, the historical poses and the map are corrected through a graph optimization algorithm to realize synchronous positioning and composition of the robot. According to the method, while the local positioning precision is ensured, the historical poses and maps are stored and corrected, accumulated errors in an outdoor long-distance environment are effectively reduced, and then synchronous positioning and composition of the robot with good global consistency are achieved.