By comparing the test between Campbell-Stokes,Jordan sunshine recorder and pyrheliometer,the threshold value of Campbell-Stokes sunshine recorder is 120W·m^-2or so.IRSR which is defined by WMO is right.The record of Jordan is 5% less than that of Campbell-Stokes and most of this error appear at sunrise or sunset.In the main,Jordan is suitable for routine observations.Pyrheliometer can be used as standard of threshold value.If the deviation of tracking sun is overcome,it can be used as a sunshine sensor,or the accuracy is hard to meet the demands.