A data writing method for a rewritable non-volatile memory module is provided. The method includes grouping physical erasing units of a rewritable non-volatile memory module at least into a first area and a second area, wherein the second area is programmed with a single-page programming mode and the first area is programmed with a multi-page programming mode. The method further includes receiving first data; and determining whether the number of a physical erasing unit having only part of physical programming units being programmed among the physical erasing units of the first area is less than a predetermined value, and if yes, writing the first data into the physical erasing units of the second area.