Heat pump is a device that transfers the heat energy from low heat source to high heat source, and it is also a new energy technology that attracts worldwide attention. It is different from the familiar mechanical equipment - "pump" which can improve potential energy; heat pump usually obtains low-grade heat energy from the air, water or soil in nature, and then provides people with high-grade heat energy which can be used after doing work by electricity. The working principle of heat pump is a mechanical device that forces heat from low-temperature object to high-temperature object by reverse circulation. It only consumes a small amount of reverse circulation net work, and can get a larger amount of heat supply. It can effectively use the low-grade heat energy which is difficult to apply, and achieve the purpose of energy saving.