The definition of triangle shape variable is provided and a novel algorithm based on triangulated irregular network (TIN) for edge detection from airborne LiDAR data is proposed. The TIN is generated in LiDAR data. Each triangle shape variable of TIN is calculated, and the edge triangle is determined according to the different triangle shape variables. These edge triangles are processed to obtain edge points. In view of the LiDAR with blank data area which may be caused by rivers etc., in which case the edge points can not be detected only by the triangle shape variable, using the sum of the quadratic distance from the three vertices to the center of gravity as a measure to determine the skinny triangle is put forward. The experimental results show that the proposed algorithm performs well to extract the edge points and obtain the edge information from the LiDAR data.