A method applied into a memory controller coupled between a memory device and a host device wherein the memory device supports at least two different storing modes includes: receiving and buffering data transmitted from the host device; using a first storing mode to store a first data unit into the memory device, a size of the first data unit being not larger than a size of a specific storage unit defined in the memory device; and using a second storing mode, different from the first storing mode, to store a second data unit into the memory device, a size of the second data unit being larger than the size of the specific storage unit.