Considering the Moon as a reference source for thermal emissive band (TEB) calibration without any knowledge of lunar surface’s emissivity or temperature, the quantitative relationship of the measured radiances between different TEBs is established by introducing the parameter universal dual-band emissivity ratio (UDER) and further used to deduce a novel cross-calibration approach between different bands. Meanwhile, selecting the thermal infrared band with the higher radiometric accuracy as a baseline, the on-orbit radiometric calibration for water-vapor band of FY-2E satellite is basically realized by using multi-bands lunar observations without any space-borne full-path blackbody. The radiometric calibration accuracy has been averagely improved by about 3.5K in the lower temperature region between 200K and 220K, which greatly benefits to the enhancement of some quantitative products significantly, i.e. cloud classification.