Abstract: In order to manage the NandFlash memory space effectively, a set associative mapping method with single replacing block is presented. The NandFlash erasable blocks is divided to several virtual block sets. When the logical space is mapped to the virtual space, the logical pages in one block set are mapped to any virtual pages in the same one block set, and the logical sets are mapped to the virtual sets one by one. Only one replacing block is set in one virtual set, which is used to withdraw and reuse the invalid pages. This method can raise the storage space utilization ratio and assure the time consumptions of the garbage withdrawing. Only the required mapping tables have to load into the memory due to the locality of the data accessing, which decreases the memory usage. The analysis results show that 16 blocks is appropriate in one virtual set for engineering practice.