The present invention provides a method for managing a flash memory module, wherein the method includes the steps of: grouping a plurality of blocks within the flash memory module into a plurality of groups; scanning a target block of each group, without scanning all of the blocks within the group, to determine if at least a portion of blocks of the group needs to be refreshed, wherein the group that is determined that at least the portion of blocks needs to be refreshed is marked as a marked group; only scanning at least the portion of blocks of the marked group, without scanning the groups that is not marked, to determine which block needs to be refreshed, wherein the block that is determined to be refreshed is marked as a marked block; refreshing the marked block(s) by moving valid data of the marked block(s) to at least one blank block.