The invention discloses a light source system for radiometer calibration. The light source system that is used for calibration of a bolometer, a radiant heat flow meter, a total radiometer, a full-spectrum radiometer, a radiation sensor and the like under the conditions of high color temperature and high irradiance comprises a radiation light source, a radiation light source connecting piece, an inner reflection shell, an outer structural shell, a rear flange, a front flange, a radiation regulator, an inner light guide arm, an outer light guide arm, a switch baffle and a cooling pipeline. Theradiation light source emits light radiation, the light radiation emitted by the radiation light source is collected through the inner reflection wall and the collected light radiation is converged and radiated forwards; the light radiation is led out through the inner light guide arm, the space of a radiation light field is homogenized, and the irradiance and the irradiation spectrum are adjustedthrough the irradiation adjuster; and a gap is formed between the inner reflection shell and the outer reflection shell and a refrigerant is used for cooling. According to the invention, a uniform irradiation field of over 50 kW/m<2> under the high color temperature can be provided; the light source system has advantages of being high in radiation illuminance, high in irradiation field uniformity, high in energy efficiency, free of background radiation interference and the like; and the calibration limit of the radiometer can be extended and the accuracy can be improved.