1. A method for compressing and decompressing three-dimensional point cloud data comprises the steps of: receiving the point cloud data; managing said point cloud data to transform said point cloud data into a regular data set; storing said regular data set in a three-dimensional grid of size M×N×P, wherein M, N, P each represents size of each dimension of said three-dimensional grid; rearranging the three-dimensional grid into a two-dimensional grid which includes said regular data set, wherein the two-dimensional grid includes M×N×P grids therein; compressing said regular data set in the two-dimensional grid by transforming said regular data set to a compressed data set; and retrieving the point cloud data by utilizing a decompression method, said method comprising the steps of: transforming said compressed data set to said regular data set; rebuilding the three-dimensional grid which includes the regular data set, from the two-dimensional grid; and according to data in the regular data set, computing a plurality of points which approximate the point cloud data.