In this study, the authors utilized infrared emission spectroscopy to investigate the infrared emission spectrum characteristics of a kind of natural carbonate and primary phase compositions, highlighting the radiation mechanism of carbonate rock. X-ray diffraction (XRD) and Raman spectroscopy results indicate that micro-nanoscale dolomite (70%), calcite (25%) and quartz (5%) are the primary phase compositions, with a small amount of iron manganese oxide. On the basis of blackbody radiation theory and the radiation energy spectra of samples from 400 to 2 000 cm^-1 at 80℃, the corresponding emissivity of this rock, pure dolomite, calcite and quartz are calculated as 1.010, 1.000, 0.997 and 0.958, respectively. Notably, the radiation energy spectrum calculated by emissivity and emission spectrum of dolomite shows high consistency with that of the natural carbonate at the same temperature, indicating that the radiation performance of the rock is mainly attributed to dolomite. Within the temperature and wavelength of this study, the heat capacity values of above minerals are the function of temperature and exhibit a positive correlation with infrared emissivity, and the highest heat capacity of dolomite benefits the enhancement of the whole thermal radiation performance of carbonate rock. The diameter of the mineral particles has a certain influence on the propagation of thermal radiation. When the diameter of particles is close to radiation wavelength, the attenuation of thermal radiation would decrease emissivity. The vibration of C-O and Si-O bonds in the narrow absorption band of emission spectrum (1 350~1 500 cm^-1 and 950~1 275 cm^-1) would lead to relatively high radiation energy and emissivity. This study can provide theoretical reference for infrared radiation material, i.e., using the rich and cheap natural minerals on the earth as a source of raw materials for infrared functional materials.