A method for reprogramming data, performed by a processing unit, is disclosed to include at least the following steps. When a page data has failed to be programmed into a first block of a storage unit and the failed page is an upper page of the first block, a host page number associated with a first lower page of memory cells of the first block of a wordline is obtained, where the memory cells comprises the failed page. When the failed page is an upper page, data from the first lower page to the upper page of the first block is programmed into a second block of the storage unit.