Abstract: Radiance uncertainties of common temperature blackbodies determine the detection accuracy of infrared optoelectronic dectetor systems. To improve the on-site calibration accuracy of blackbodies'radiance, a standard radiometer was used to calibrate three blackbodies, including one cavity blackbody and two surface blackbodies. The standard radiometer was traced to a standard blackbody hold by National Institute of Metrology of China and obtain a uncertainty of less than 0.22%. Brightness temperatures and effective emissivities were acquired by measuring three blackbodies'radiance directly. The results show deviations of 0.6 K to 2.6 K between brightness temperatures and setting temperatures for all three blackbodies, which correspond to absolute radiance uncertainties from 1.4% to 5.5%. The direct calibration method based on standard radiometer avoids the uncertainties from measurements of temperature and emssivity, and can be used to realize on-site system-level calibrations of blackbodies and absolute radiance monitoring.