A method for writing updated data into a flash memory module having a plurality of physical pages is provided, wherein each physical page is the smallest writing unit of the flash memory module. The method includes partitioning a physical page into storage segments and configuring a state mark for each storage segment, wherein the state marks indicate the validity of data stored in the storage segments. The method also includes writing the updated data into at least one of the storage segments and changing the state mark corresponding to the storage segment containing the updated data, wherein the state mark corresponding to the storage segment containing the updated data indicates a valid state, and the state marks corresponding to the other storage segments of the physical page not containing the updated data indicate an invalid state. Thereby, the time for writing data into a physical page is effectively shortened.