A memory system includes: a memory device; and a controller suitable for performing: a free block management operation of detecting victim blocks onto which a garbage collection operation is to be performed to generate required free blocks; a garbage collection operation time management operation of calculating an estimated garbage collection operation time for the detected victim blocks; and a garbage collection operation period management operation of dynamically changing a garbage collection operation period based on the estimated garbage collection operation time and periodically performing a garbage collection operation based on the garbage collection operation period during a specific time, wherein the controller repeatedly performs, whenever an update period arrives, the free block management operation, the garbage collection operation time management operation, and the garbage collection operation period management operation.