Abstract: A four-spectral infrared radiometer, which can automatically measure the temperature of sea surface, was designed to calibration and test the satellite on ground. The electronics system of the infrared radiometer was designed in detail using the spectral modulation, the wave length of 3.5-4 m, 8-13 m, 10.3-11.3 m, 11.5-12.3 m infrared band was used to acquire and process the data. The temperature of the sea surface was computed by double blackbody standard source real-time automatic correction system parameters and corresponding algorithm. The designed infrared system could also display the temperature and save the data synchronously on PC. In addition, the requirement of sampling precision of 0.1K was guaranteed by the design of A/D sampling. Finally, by analying the data acquired in south China sea, the measure precision of the system was verified in 0.5 K, which can satisfy the technical requirement.