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The spatial and temporal distributive characteristics and variation trends of precipitable water in the southwest area are analyzed by using NCEP monthly precipitable water data from 1980 to 2009 The results show that influenced by geographical environment and climate,the distribution of annual and seasonal precipitable water in Southwest China has obvious regional difference, greater in the southeast and less in the northwest.Precipitable water varies with season obviously, with the value in summer being visibly higher than that in winter, and that in autumn slightly higher than that in spring.The annual distribution of precipitable water is uneven: the greatest precipitable water appearing in July, the secondary in August, and the least in January. Around the recent 30 years, the annual precipitable water in the southwest fluctuates alternately. There is an upward trend in annual precipitable water, as well as in spring and winter. The spatial distribution of annual precipitable water exhibits not only consistency in the whole area, but also reverse patterns.