In view of the effective results about the long term disaster weather prediction based on the variation of the earth rotation in the recent 10 years,  the authors try to explore the deep reason of major disaster weather with the re lationship among the earth nutation,  rotation and atmospheric change.  The relationship between the subtropical anticyclone and subtropica l easterlies is discussed,  aiming at the problem of high temperature and drought in the globe.  Further more,  the comparison analysis is made on earth nutation and the variation of rotation.  The research results show that the reasons of important disaster weather not only involre atmosphere itself,  but have some variation information of earth movement which could be used for the weather forecast.