Lunar radiometric characteristics make the moon an possible exoatmospheric longwave infrared reference. The physical temperatures of the subsolar area can be calculated accurately by the "radiative equilibrium thermal model ", which are in good agreement with the measurements of Diviner. The emissivity of lunar regolith in the longwave infrared spectrum is between 0.9 and 0.98, and the average of 0.95 can be used. Directional characteristics of lunar longwave infrared emissivity should be considered if high accuracy is pursued. For using of the moon as an exoatmospheric longwave infrared reference, generally the "radiative equilibrium thermal model and mean emissivity can meet the application. In the case of high precision, the infrared brightness temperatures of Diviner can be used to establish a database with certain spatial resolution. The advantages of this approach are obvious; cameras with small aperture can be used to measure the moon.