A memory system includes: a plurality of memory devices, each of which includes a first block and a second block; and a controller suitable for: storing data received from a host in a buffer; selecting a first block, of a memory device of the plurality of memory devices, to be programmed with the data; detecting a size of the data; controlling the memory device to program the data into the selected first block when the size is detected to be equal to a one-shot program size; determining a status of the memory device including the selected first block when the size is detected to be smaller than the one-shot program size; controlling the memory device to program the data into the selected first block when the memory device including the selected first block is determined to be in a first status; and controlling the memory device to program the data into the second block of the memory device when it is determined to be is a second status.