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By analyzing and evaluating the uncertainty of the provincial working standard pyranometer tracing to World Radiometric Reference,the main uncertainty sources are given such as the measurement repeatability, voltage output, the change of incident angle, thermal offset and the standard instrument. The expand uncertainty of calibration results for the provincial working standard pyranometer is 06%. The provincial working standard pyranometer is calibrated using the component summation method in China. The proportion of uncertainty component caused by standard instruments is over 90%. So the key to reduce the uncertainty of traceability is to reduce the measurement uncertainty of the direct radiation standard (03%) and diffuse radiation standard (10%). The accuracy for solar radiation measurement is also greatly impacted by weather conditions. Choosing the stable weather with good atmospheric transparency and solar altitude angle over 30° and increasing the number of measurements can decrease the data dispersibility and reduce the uncertainty component caused by the measurement repeatability; the thermal offset can be reduced by ventilating the calibrated pyranometer. The proper installation of instruments such as ensuring the level of sensors and suntracking accurately with a shading system can further reduce the uncertainty of traceability and improve the accuracy of shortwave radiation measurement.