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Five calibration methods of pyranometers are introduced and their advantages and disadvantages are compared. For different classes of pyranometers, there are different calibration methods to transfer values in order to meet the needs of different customers. By comparison of different methods, the results show that the sensitivity accuracy of the pyranometers calibrated by the shaded/unshaded method is better than those by using the component summation technique. Likewise, the component summation method is better than the sidebyside comparison method. The error of the method using an artificial source to calibrate pyranometers in the laboratory is the maxmium. According to WMO CIMO Guide, pyranometers should be calibrated only in the position of using sun as light source. The shaded/unshaded method is used to calibrate the national diffuse irradiance standard pyranometer, and the component summation method to calibrate the provincial standard pyranometer, the side by side comparison method to calibrate the working pyranometer in stations. All these methods ensure the accuracy and reliability of solar radiation measurement data.