The measure method of Solar Irradiance Absolute Radiometers(SIARs) is investigated and revised in order to extend the dynamic measurement range and improve the measure uncertainty of lower laser power. The sensitivity of each laser power was repeatedly measured. The impact of the system error of sensitivity on the measure uncertainty was analyzed. The revised method was proposed. The sensitivity in the narrow power interval and near the optical power was corrected pass through two electrical calibrations. Different laser powers were measured with the new method and the traditional method. The measure uncertainties were compared. Experimental result indicate that the relative uncertainty of the sensitivity achieved from the wide power interval is 2.7%. The system error of sensitivity cannot be neglect when measuring lower laser power. When laser power is lower than 20 mW, the relative measure uncertainty of the new method is still 0.1%. The new method possess a better stability. The error of sensitivity is compensate. Therefore, the difference between electrical and optical calibration is extremely large, and does not have comparability. The total dynamic range calibration needs the combination of electrical and optical calibration. The dynamic measurement range is extend by the new measure method, which is significant for calibrating SIRAs.