A method of optical radiometric calibration based on correlated photons was proposed to improve calibration precision. It was independent of the methods based on radiometric source or detectors. With 351 nm laser to pump β-Barium Borate(BBO)crystal, a radiometric calibration system based on correlated photons had been set up, and its principle and experimental setup were analyzed. Coincident metrical system was given, and the experimental result is discussed. The results showed that the calibrated quantum efficiency of photomultiplier (R2949) at 702 nm was (5.96±0.003)% , the relative error of experimental result was about 1.0% with respect to the typical quantum efficiency of photomultiplier (R2949)at this wavelength, and relative combined uncertainty of the results was about 2.61%.