The invention provides a data cache method used in NAND FLASH. The method comprises following steps: first, a cache region cache is divided into a block-level cache and a page-level cache; then, when read-and write is performed on data, if current data exists in the block-level cache or the page-level cache, then data read-and write is directly completed; if current data does not exist in the block-level cache or the page-level cache, then data is read from the FLASH or free space in the data cache region is distributed to the current data and data is written in the FLASH; if there is no free space, a substitution block is determined through a substitution algorithm and data in the substitution block is written in the FLASH; finally, the substitution block is released, new data is written in, and then data cache is completed. By means of the combination of block cache and page cache, the cache hit ratio of random read-and-write access is increased; a efficient substitution algorithm is provided; the size of cache mapping table is reduced and space utilization rate of the cache region is increased; the method has good use value.