We study the coldest vicarious calibration method for the Jason-2 Microwave Radiometer（JMR）. We simulated the o bserved value of the global minimum brightness temperature for three JMR channels using the microwave radiation transfer theoretical calculation model. Using 2008 to 2012 Jason-2 geophysical data record data products for global earth observations of brightness temperature

we establish a statistical model for identifying the coldest brightness temperature series. We then set up a spectral analysis model

according to the annual change characteristics

to remove the annual harmonic from the coldest brightness temperature series. Using the linear fitting method

the annual harmonic is removed and then extrapolated to the theoretical minimum brightness temperature

to calculate the annual drift of the JMR instrument.