The invention provides a refrigerating and freezing device and a control method thereof. An air-conditioning preserving space is formed inside the storage space of the refrigerating and freezing device, and an electromagnetic lock is arranged on the door body of the air-conditioning preserving space. The control method comprises the following steps: detecting whether the door body of the refrigerating and freezing device is opened or not; connecting a power supply to the circuit of an electromagnetic coil if the door body is opened, and permitting the power supply to supply electricity; and disconnecting the power supply to the circuit of the electromagnetic coil if the door body is not opened, and forbidding the power supply to supply electricity. According to the method, only when the door body of the refrigerating and freezing device is opened, the power supply of an electromagnetic lock and the electromagnetic coil are connected, and the power supply is permitted to electrify the electromagnetic coil; and when the door body of the refrigerating and freezing device is closed, the circuit switch is disconnected, and the electromagnetic coil and the power supply are in a disconnected state. By the arrangement, long-time connection of the power supply and the electromagnetic coil can be prevented, and the potential hazard of electric shock when a user uses the refrigerating and freezing device can be reduced.