Abstract: The calibrations of radiometer is a technology that is taken primary source and a absolute radiometer primary radiometer as a highest standard.It calibrates standard detector by this standard,then using this standard to calibrate common detectors.The basic equipment for radiometic calibrating is a set of standard radiometer and primary standard source.In this paper,we introduce the fundamental principle of the calibrating a detector with the standard radiometrer and discuss is the selection of the working standard for increasing the spectral resolution.By discussing the above problem,we expect to resolve how to select the best detector and source.we make a list of of all possible detectors or sources and their features to make sure source and detector are the best.