1. A data classification system, comprising: a fetch unit, for receiving data including at least one datum, and fetching a data information contained in the data, wherein the data information comprises a coordinate information, and the coordinate information comprises a longitude and a latitude; a classification tree module, for classifying the data in a manner of a tree structure according to the data information, and building a classification tree, wherein the classification tree comprises a plurality of nodes, each comprising a center position, a maximum distance of the data in the node to the center position; and a data repository, for storing the classification tree and the data, wherein the classification tree module obtains the data and adds it into a node, then calculates the center position of the node according to the coordinate information corresponding to the data, a distance of the coordinate information of each of the data to the center position, and obtains the maximum distance, thereafter determines whether the maximum distance is greater than a predetermined distance, if the maximum distance is greater than the predetermined distance, the classification tree module calculates a maximum longitude difference and a maximum latitude difference of the data according to the longitude and the latitude of each of the data, if the maximum longitude difference is greater than the maximum latitude difference the classification tree module arranges all data according to the longitudes thereof, and takes a longitude median of the data as a center to divide the node into a first sub-node and a second sub-node, and if the maximum longitude difference is smaller than the maximum latitude difference, the classification tree module arranges all data according to the latitudes thereof, and takes a latitude median of the data as a center to divide the node into the first sub-node and the second sub-node.