A plane source blackbody is provided. The plane source blackbody comprises a panel, a black lacquer, and a carbon nanotube layer. The panel comprises a first surface and a second surface, and the first surface is opposite to the second surface. The black lacquer is located on the first surface. The carbon nanotube layer is located on a surface of the black lacquer away from the first surface. A method of making the plane source blackbody is also provided.