The present invention generates the file similarity generating similarity hash value on the basis of the anchor to reduce the overhead of file synchronization to a system and method, a file synchronization system, considering the energy efficiency according to the present invention, the hash calculated considering the energy efficiency client device and a similarity comparing unit for unit already stores the received file server storage from a client device and, compared to the similarity with the one similarity hash value received from the file, the similarity generation unit is stored in the server storage unit hash values ​​including a and, removed when the file having a certain or more degree of similarity are found in the similarity comparing unit by including a server device the variable-length including a chunking and energy efficiency calculations for a fixed-length calculation chunking related energy efficiency, by measuring the deduplication-related energy consumption duplicate You may select the method.