Atmospheric correction microwave radiometer (ACMR) is one of the main payloads for correcting atmospheric path delay of radar altimeter on HY-2A satellite. After discussion and analysis on thermal vacuum calibration method of ACMR, microwave transfer functions and related coefficients were given, especially nonlinear coefficients derived from the test for correcting nonlinear responds between the input of antenna temperature and the output of voltage at each channel of ACMR. Meanwhile, antenna pattern correction algorithms for removing the effects of side-lobe and cross-polarization were derived and their coefficients were used for in-orbit data processing. The calibrated antenna temperatures were compared with the similar space-borne microwave radiometer on Jason-1 and Jason-2 satellite (JMR), launched by the NASA-French Space Agency Ocean Surface Topography Mission. The results of comparison showed that the data from ACMR were well matched to those from Jason-1 and Jason-2.