The invention provides an energy-saving device capable of automatically adjusting brightness and heat flow and shielding infrared radiation. The energy-saving device comprises a bimetallic strip, a support frame, glass and the like. The bimetallic strip is bent at high temperature and blocks sunlight, the sunlight entering an indoor environment is reduced, indoor brightness is reduced, indoor radiation heat gains are reduced, an airflow channel can be formed in the device or a thermal bridge between pieces of the glass is interrupted, and heat transferred from the device to the indoor environment is reduced. The bimetallic strip unbends at medium temperature, blocking of the sunlight is reduced, the sunlight entering the indoor environment is increased, the indoor brightness is improved, the thermal bridge is conducted, and heat transfer coefficients of the device are increased. The bimetallic strip is bent at low temperature and shields infrared radiation from the indoor environment to an outdoor environment, indoor heat dissipation is reduced, the thermal bridge is interrupted, and the heat transfer coefficients of the device are reduced. The device can automatically adjust the indoor brightness and indoor heat gains and shield infrared radiation according to change of solar radiation and outdoor temperature, and energy consumption of daylighting, air conditioning and heating of a building is reduced.