Following the development of the embedded system, the requirement of the NAND type flash memory equips is higher and higher. Taking the NAND flash as an example, the application and design of the large capacity NAND Flash in embedded system is presented. A method for eliminating the influence of the bad block appearance when the file is writting is put forward, The algorithm of the management softwore FMM based on the NAND Flash is optimized. And then the efficiency and performance are enhanced.