The present invention relates to a blackbody radiation source. The blackbody radiation source comprises a blackbody radiation cavity and a plurality of carbon nanotubes. The blackbody radiation cavity comprises an inner surface. A carbon nanotube array located on the inner surface of the blackbody radiation cavity. The carbon nanotube array comprises a plurality of carbon nanotubes, and an extending direction of each carbon nanotube is substantially perpendicular to the inner surface. The carbon nanotube array comprises a first surface and a second surface. The first surface is in contact with the inner surface and the second surface is far away from the inner surface. The plurality of carbon nanotubes extend from the first surface to the second surface. A plurality of microstructures are formed on the second surface of the carbon nanotube array.