The traditional scanning method of photon counting three-dimensional (3D) imaging is point-by-point sampling. According to the quadtree block method, an adaptive contour extraction method used in 3D time-concerned-single-photon-counting (TCSPC) lidar is proposed. The adaption of method is showing as followed. When an unknown target area is sampled, the size of scanning step varies according to the surface continuity of the target area. The scanning method applied in this paper scans the unknown target area with non-uniform steps and then reconstructs the target image according to the difference of surface continuity. The experimental results show that the sampling method in this paper can effectively reduce the number of samples in the unknown target area while ensuring the details of the target contour, thus improving the imaging efficiency.