As one emerging plasmonic material,graphene can support surface plasmons at infrared and terahertz frequencies with unprecedented properties due to the strong interactions between graphene and low frequency photons.Since graphene surface plasmons exist in the infrared and terahertz regime,they can be thermally pumped(excited)by the infrared evanescent waves emitted from an object.Here,we show,for the first time,that thermal grapheme plasmons can be excited with a remarkable efficiency of about 90%and have monochromatic and tunable spectra,thus paving a way to harness thermal energy for graphene plasmonic devices.We further demonstrate that we can potentially realize "thermal information communication" via grapheme surface plasmons by effectively harnessing thermal energy from various heat sources,e.g.,the waste heat dissipated from nanoelectronic devices.These findings open up a new avenue of thermal plasmonics based on graphene for different applications,ranging from infrared emission control,to information processing and communication,and to energy harvesting.