Abstract: A new absolute calibration method based on the parametric down-conversion was introduced. In the parametric down-conversion process, two correlated-photons were produced whose wavelengths were 0.631 m and 3.39 m, the average photon countsper mode of the 3.39 m were obtained by measuring the ratio of 0.631 m photon counts in the two processes including the spontaneous parametric down-conversion and the stimulated parametric down-conversion, and further radiance of the infrared source could be calculated. In this paper, the calibration principle and experimental device were described and the uncertainty of this method was analyzed. The results show that relative combined uncertainties of a OPO laser was better than 1.18% and prove the feasibility of radiance calibration of the infrared radiation by detecting the photon counting in the visible band. The study results are expected to be used in the field of high precision calibration of infrared band based on stimulated parametric down-conversion and infrared OPO laser and other fields.