Aiming at improving the efficiency of point cloud boundary extraction method，based on micro-cut surface in LiDAR point cloud， and to ensure the fineness and integrity ofboundary extraction， an a-shapes algorithm of adjustable rolling circle radius is proposed todeal with plane point cloud boundary.The algorithm firstly rasterized point cloud data andthen excluded non-boundary points.Thirdly， rolling round radius was set by a regulatoryfactor and the average distance between K adjacent points of P.Finally， a-shapes algorithmwas utilized to extract the point cloud boundary.To analyze the relationship among the knearest neighbors， point cloud shape and point cloud density， it is proved that there is a func-tional relationship between the K value and the regulating factorω.And the regulatory fac-to r is independent of point cloud density and point cloud shape.The results showed that thisalgorithm can quickly extract the complete point cloud boundary and improve the speed andefficiency of subsequent point cloud reconstruction under the condition of accurately extrac-ting the point cloud boundary， with good robustness.