A program method for a multi-level cell (MLC) flash memory is provided. The memory array includes a plurality of pages and a plurality of paired pages, which correspond to the respective pages. The program method includes the following steps. Firstly, a program address command is obtained. Next, whether the program address command corresponding to any one of the paired pages is determined. When the program address command corresponds to a first paired page, which corresponds to a first page among the pages, among the paired pages, data stored in the first page to a non-volatile memory are copied. After that, the first paired page is programmed.