A flash memory controller refreshes memory blocks in a flash memory device by setting different refresh cycles for individual memory blocks in the flash memory device. The flash memory controller records a number of erase operations performed on each memory block of the flash memory device. Upon detecting that a bit error rate of a memory block is greater than a preset threshold, the flash memory controller determines a refresh cycle for the memory block based on recorded number of erase operations performed on the memory block, and then refreshes the memory block according to the refresh cycle.