The paper proposes to judge the working condition of a ground-based microwave radiometer for atmospheric remote sensing by observing the brightness temperature (TB) at 08:00 BST on clear days according to atmospheric temperature seasonal variation features.Radiative transfer theory was briefly introduced and the data of temperature at 08:00 BST observed at Nanjing during the period of November 27,2010 to May 29,2011 were used to make a statistical comparison between the observed TB with a ground-based microwave radiometer and the simulated TB with radiosonde profiles as input to radiative transfer calculation in order to judge the working condition of the radiometer.The radiometer has 12 channels including 5 channels at 22.235,23.035,23.835,26.235 and 30.000 GHz for sensing humidity and liquid water content and 7 channels at 51.25,52.28,53.85,54.94,56.66,57.29 and 58.80 GHz for sensing temperature profiles.The results showed that the former 5 channels worked well in the period while the latter 7 did not.The methodology may be applied to radiometers' working condition monitoring as well as observation data quality control.