Abstract: Aiming at the technical problems appearing in the field of infrared metrology, that is, how to build up a testing facility to calibrate infrared imaging systems and to trace back to the quantity value, a calibration facility of the testing subsystems in infrared imaging systems to measure the differential temperature transmittance with a precision temperature measurement scanning radiometer was achieved. Proceeding from the differential temperature and its transfer ratio, the model of differential temperature transfer ratio produced by blackbody and highresolution target is analyzed. The complexity of the model resulted from two largearea blackbodies is introduced. The effect of temperature difference transmittance of the testing system for infrared imaging systems on SiTF，MRTD and MDTD of infrared imaging systems is pointed out in this paper. The scientificalness of the scheme for the calibration of the testing facility is verified.