The invention introduces a method for programming data of page groups into flash units to include steps for: obtaining, by a host interface (I/F) controller, user data of a page group from a host side, wherein the page group comprises multiple pages; storing, by the host I/F controller, the user data on the pages in a random access memory (RAM) through a bus architecture, outputting the user data on the pages to an engine via an I/F, and enabling the engine to calculate a parity of the page group according to the user data on the pages; obtaining, by a direct memory access (DMA) controller, the parity of the page group from the engine and storing the parity of the page group in the RAM through the bus architecture; and obtaining, by a flash I/F controller, the user data on the pages and the parity of the page group from the RAM through the bus architecture, and programming the user data on the pages and the parity of the page group into a flash module.