Based on Delaunay triangular mesh method, a LiDAR point cloud building edge extraction algorithm is put forward in this paper. First of all, filter LiDAR point cloud and extract the building points. Then establish a triangular mesh according to Delaunay method, and calculate the length of each triangular mesh, to get an average side length. Taking the average side length as threshold, when a triangle’s side length exceeds the threshold, its three points are considered as edge points. In this triangle, the short side is usually the building edge outline, whose length is less than the threshold. After linking the short side, the building edge circuit is obtained. Since building usually occupies larger space than the other surface features, the circuit with more points is kept, and then the building outline of building can be formed by using pipe algorithm for normalization. The processing result on the experimental airborne LiDAR point cloud data shows that the algorithm can extract the building edge quickly and efficiently from LiDAR point cloud data.