Abstract: The cooling rate of Nitric Oxide is calculated by using recently developed empirical formula of Nitric Oxide density.The effeCt of solar and.geomagnetic activity on Nitric Oxide cooling rate is studied.The main results obtained are:(1)the cooling rate and the height of maximum cooling rate occurrence periedicly varies with solar activity;(2) the variation rule with solar zenith angle are not symmetry.before and after noon;(3) it is found that the cooling rate of Nitric Oxide is not only larger than Oxigen atoms,but also its response to solar and geomagnetic activity is far more sensitive than Oxigen atoms. It is proved that Nitric Oxide cooling is a major cooling process above 120Km in the thermosphere.