The presence of interlayer interactions in twisted bilayer graphene(TBG) enhances several characteristics, including the optical and electronic properties. We theoretically investigate the magic angle of TBG according to the vanishing of Fermi velocity and find double magic angles in a series. Thermal radiation from TBG can be tuned to the far infrared range by changing twist angles. The peculiar radiation spectrum is out of atmospheric window, which can be of great use in invisibility and keeping warm. The total radiation of TBG is slightly more than twice of a single layer graphene.