A memory control circuit unit including a plurality of data randomizer circuits and a data selection circuit is provided. When a first data stream is received from a host system, the first data stream is input into the data randomizer circuits to respectively output a plurality of second data streams. The data selection circuit selects one of the second data streams as a third data stream according to contents of the second data streams, and the third data stream is programmed into a rewritable non-volatile memory module. Accordingly, data written into the rewritable non-volatile memory module can be effectively disarranged.