The invention introduces a method for executing host input-output (IO) commands, performed by a processing unit of a device side when loading and executing program code of a first layer, at least including: receiving a host IO command from a host side through a frontend interface; generating a slot bit table (SBT) including an entry according to the host IO command; creating a thread of a second layer; and sending addresses of callback functions and the SBT to the thread of the second layer, thereby enabling the thread of the second layer to call the callback functions according to the IO operation of the SBT for driving the frontend interface to interact with the host side to transmit user data read from a storage unit to the host side, or receive user data to be programmed into the storage unit from the host side.