Abstract: The calibration of radiometric sensors is critical to ensure the accuracy of the remote sensing data and their usability. The current methods of the radiometric calibration are based on the establishment of high precision primary standard and standard transfer chain, and the transfer chain is the main source of errors. The entangled photons-based theory creates a new technical way to realize the radiometric calibration of “standardless transfer”. The method of absolute calibration of photodetectors based on a nonclassical effect of the nonlinear optics in the photon-counting regime was discussed. The measurement was realized with the technique of entangled photons at 702nm generated by a parametric down conversion process in a nonlinear crystal of BBO. The photomultiplier quantum efficiency at the wavelength was measured during the experiment. It is estimated that the deviation is 0.1%. The technique is independent of any externally calibrated radiometric standards.