A data backup method, wherein the method comprises the following steps: obtaining, by a backup server, an original differential bitmap of a first target volume from a production end, wherein the first target volume is a to-be-backed-up volume, and the original differential bitmap is an original differential bitmap of all fixed-length data blocks in the first target volume, wherein the original differential bitmap was generated when data in the first target volume changes and each of the fixed-length data blocks corresponds to one bit in the original differential bitmap; obtaining valid data in the fixed-length data blocks from the first target volume according to the original differential bitmap; saving a bitmap corresponding to a fixed-length data block comprising the valid data to a fixed-length volume bitmap file of the fixed-length data block according to the original differential bitmap, wherein the bitmap corresponding to a fixed-length data block comprising the valid data is a subset of the original differential bitmap, and the fixed-length volume bitmap file is used to identify a storage address of the valid data in the first target volume; saving the valid data in the fixed-length data block to a fixed-length volume file of the fixed-length data block, wherein the fixed-length volume file and the fixed-length volume bitmap file are in one-to-one correspondence and are saved in association, and the fixed-length volume file is used to store the valid data in current backup; saving a volume mapping file of the first target volume according to the fixed-length volume file, wherein the volume mapping file comprises at least a name of the fixed-length volume file of the fixed-length data block in the first target volume and a storage path of the fixed-length volume file; obtaining, by the backup server, an incremental bitmap of the first target volume from the production end, wherein the incremental bitmap is a differential bitmap of a changed fixed-length data block in the first target volume; obtaining valid data in the changed fixed-length data block from the first target volume according to the incremental bitmap; saving a bitmap corresponding to a fixed-length data block comprising the valid data to a fixed-length volume bitmap file of the fixed-length data block according to the incremental bitmap; and saving the valid data in the fixed-length data block to a current fixed-length volume file of the fixed-length data block. obtaining, by a backup server, an original differential bitmap of a first target volume from a production end, wherein the first target volume is a to-be-backed-up volume, and the original differential bitmap is an original differential bitmap of all fixed-length data blocks in the first target volume, wherein the original differential bitmap was generated when data in the first target volume changes and each of the fixed-length data blocks corresponds to one bit in the original differential bitmap; obtaining valid data in the fixed-length data blocks from the first target volume according to the original differential bitmap; saving a bitmap corresponding to a fixed-length data block comprising the valid data to a fixed-length volume bitmap file of the fixed-length data block according to the original differential bitmap, wherein the bitmap corresponding to a fixed-length data block comprising the valid data is a subset of the original differential bitmap, and the fixed-length volume bitmap file is used to identify a storage address of the valid data in the first target volume; saving the valid data in the fixed-length data block to a fixed-length volume file of the fixed-length data block, wherein the fixed-length volume file and the fixed-length volume bitmap file are in one-to-one correspondence and are saved in association, and the fixed-length volume file is used to store the valid data in current backup; saving a volume mapping file of the first target volume according to the fixed-length volume file, wherein the volume mapping file comprises at least a name of the fixed-length volume file of the fixed-length data block in the first target volume and a storage path of the fixed-length volume file; obtaining, by the backup server, an incremental bitmap of the first target volume from the production end, wherein the incremental bitmap is a differential bitmap of a changed fixed-length data block in the first target volume; obtaining valid data in the changed fixed-length data block from the first target volume according to the incremental bitmap; saving a bitmap corresponding to a fixed-length data block comprising the valid data to a fixed-length volume bitmap file of the fixed-length data block according to the incremental bitmap; and saving the valid data in the fixed-length data block to a current fixed-length volume file of the fixed-length data block.