Disclosed is an operating method of a memory system that includes a plurality of memory blocks, the operating method including a first step of copying, in order to recover sudden power-off of the memory system, data of an open block to a selected block among the plurality of memory blocks while maintaining map data associated with the open block and open block identification information; a second step of erasing the open block; and a third step of copying the data, which is copied to the selected block, to the erased open block.