A method and system for achieving data de-duplication on a block-level storage virtualization device belonging to the field of data storage technologies, is disclosed. The method comprises: deleting the duplicate data in the actual physical data corresponding to the specified virtual LBA address space to obtain the data extents after physical data is de-duplicated; establishing the correspondence between the virtual LBA address space and the data extents after the physical data is de-duplicated; according to the correspondence and metadata information of the data extents, obtaining the storage position information of the actual physical data corresponding to the virtual LBA address space pointed by external data read and write requests to complete the I/O redirection. This invention also provides a system for achieving data de-duplication on a block-level storage virtualization device. This invention can delete duplicate data across hosts and storage devices, to achieve a wider scope of data de-duplication.