A flash memory controller having a flash memory testing functions is provided, in which the flash memory controller includes a microprocessor unit, a flash memory interface unit, a host interface unit and a memory cell testing unit. The flash memory interface unit is configured for connecting a plurality of flash memory chips, where each flash memory chip has a plurality of flash memory dies and each flash memory die has a plurality of physical blocks. The host interface unit is configured for connecting a host system. The memory cell testing unit is configured for determining whether the physical blocks can be normally written, read and erased. Accordingly, the flash memory controller can perform a flash memory testing under a command of the host system and all the physical blocks of the flash memory chip can be tested during the flash memory testing.