The invention relates to a key data storage method for a multi-level cell NAND flash memory, comprising: requesting, by a file system, to write a first content to a first logic address; allocating, bya Flash translation layer, a first physical address to the first logic address; judging whether the first content is key data; if yes, continuing to judge whether the first physical address is an LSB(last significant bit) physical page; if yes, searching a shared mapping table for an MSB (most significant bit) physical page corresponding to the first physical address, and marking the MSB physical page as an invalid one. The key data storage method for the multi-level cell NAND flash memory has the advantages that error rate of system key data is effectively reduced, no significant influenceis caused upon storage system I/O (input/output) performance, and system reliability is improved. The invention also relates to a multi-level cell NAND flash memory and a trash recycling method of themulti-level cell NAND flash memory.