The present invention relates to a method, system, and computer program product for data backup, the method comprising: performing first chunking on current data by using the same chunking method as that used by original backup data to obtain a current chunk; calculating hash value of the current chunk; and acquiring, from a hash value table of the original backup data, an identifier of a matched chunk whose hash value is the same as the calculated hash value of the current chunk, and incrementing number of continuous matched chunks by one. Since the pertinence between original backup data and current data is maximally utilized, performance of de-duplication method can be efficiently improved.