A controlling method for a memory storage device is provided. The method includes: disposing a rewriteable non-volatile memory module which is operated at a first working voltage in the memory storage device; and detecting whether the first working voltage is lower than a first voltage threshold. The method also includes: detecting whether a circuit component working voltage is lower than a circuit component voltage threshold; when the first working voltage is lower than the first voltage threshold, setting the memory storage device to stop executing commands from a host system and to stop giving commands to the rewriteable non-volatile memory module; and, when the circuit component working voltage is lower than the circuit component voltage threshold, enabling a reset signal to stop receiving and executing commands from the host system. Therefore, the method can effectively improve the stability of the memory storage device.