A simulating method for a flash memory and a simulator using the simulating method are provided. The simulator is configured to couple to a memory controller. The simulating method includes: setting a predetermined response condition; providing multiple command sets, wherein each of the command sets corresponds to a memory type; receiving a first command from the memory controller; identifying a second command in the command sets according to the first command; determining if the second command matches the predetermined response condition; obtaining a first signal corresponding to the second command according to the predetermined response condition; and, transmitting the first signal to the memory controller. Accordingly, the usage of the simulator is flexible.