The present invention discloses a method for controlling the smart electric appliance by connecting a key device to a smart electric appliance and performing control operations on the smart electric appliance in accordance with the control settings for the key device after positively authenticating the internal device descriptor of the key device. Also, the present invention discloses a system according to the method mentioned above, including a smart electric appliance comprising a USB interface module, an authentication module, an execution module and a general control module, and a key device comprising a smart storage module. By introducing the key device, authenticating the key device before allowance of use of the smart electric appliance, and setting different control operation levels for different users of the smart electric appliance, it becomes very secure to use the smart electric appliance, while it becomes more flexible to use the same.