A memory management method for a rewritable non-volatile memory module is provided. The memory management method includes using a first management mode to manage the rewritable non-volatile memory module after the rewritable non-volatile memory module is powered on; and using a second management mode to manage the rewritable non-volatile memory module if a shut down command is received from a host system, wherein the second management mode is different from the first management mode and the second management mode executes at least one mandatory processing procedure in background.