With the increase of point cloud data gained by three dimensional laser scanner,the reduction of laser point cloud data has been a research hotspot in the field of Geomatics Engineering in recent years.Based on layer technology research of point cloud data,an improved algorithm by expanding two-dimensional plane curve algorithm-Douglas-Peucker algorithm into three-dimensional space is proposed,which do not need to get the adjacency relation of known point cloud data before dealing with the data,thus it can deal with three-dimensional scattered point cloud data directly.A grid model by means of the Matlab platform was built to realize the reduction of the point cloud data.Compared with the grid model of the original ones,the effect of the new algorithm is better.