The invention discloses a data distribution method and system for a network data center. The method comprises the following steps: at least one node server of the network data center downloading a source file from a data source server; a download management server storing the identification of a node server which already downloads the source file; a node server, which does not download the source file, of the network data center querying from the download management server the identification of the node server which already downloads the source file; and the node server which does not download the source file establishing download connection with a queried node server which already downloads the source file and downloading the source file from the node server which already downloads the source file. By using the method, some node servers in a network data center download a source file from a data source server, and other node servers download the source file from node servers which already download the source file so that it is unnecessary for all the node servers to download the source file from the data source server, thus occupation of special-line bandwidth of the network data center can be reduced.