After analyzing the climate background,weather support difficulties,and support risks in Xichang when launching Chang E II,this paper described the meteorological support progress on that day.It found that the cold air which will work on the launching field appears after the ＂launch window＂,which provides a vital basis for the launching decision making.The results show that the meteorological support for spaceflight bears high risk.So we should increase research efforts on the meteorological information,and improve its contingency plan and decision-making on weather risk.