Abstract: To investigate the performance of InfRared Atmospheric Sounder (IRAS)aboard the satellite FY-3A, the retrieval of the vertical profile of atmospheric temperature is studied based upon the IRAS channel spectral characteristics in i ts initial design and the spectral response function of the spectrometer.The retrieval is performed using different combinations of channels for 15 μm CO₂absorption bands of the IRAS, indicating that on the w hole the sounder produces higher retrieval and inclusion of channel 8 leads to the remarkable improvement of retrieval precision of near-surface-layer temperature.For the retrieval from an iterative algorithm the first guess profile affects the precision greatly, and the closer the estimated profile to the t rue value, the higher the accuracy.The designed channel sensitivity meets the required needs of such retrieval.Low sensitivity leads to lowered precision.As a result, the retrieval precision depends strongly on the IRAS sensitivity.