The FY 2B is a satellite with the spin stabilized attitude, it is had to make the absolute calibration for its IR channel while the satellite is in orbit. As the satellite's pre launch Lab calibration had a reference on the in orbit environment temperature changes of FY 2A, its calibration is ideal. With the correction on quantitatively relationship of the IR channel by the in orbit electronic calibration, the obtained results are very close to the ones from the simultaneous site radiometric calibration over the Qinghai lake.