1. A method for modifying file contents of a flash file stored in a flash memory while balancing wear of the flash memory, the method comprising the steps of: finding first file nodes recording the file contents to be modified; searching for void file nodes in the flash memory, and selecting void file nodes as second file nodes; writing modified contents of the first file nodes to at least one of the second file nodes; building node link information of the second file nodes that have been written; marking the first file nodes with a predetermined flag; and updating node versions of the second file nodes that have been written.