A data access method capable of reducing the number of erasing to flash memory and a data patch and access device that utilizes the method are disclosed. A data write procedure is provided for determining a difference between data to be written and existed data in the data block when writing data to a data block of the flash memory, and if the difference is less than a pre-determined value, writing the difference to a patch area instead of writing the data to the data block. A data read procedure is provided for searching the difference recorded in the patch area when reading data from a data block of the flash memory, so as to patch the data.