The surface vapor content has a close correlation with the generation of precipitation.Based on the atmospheric circulation data and surface vapor content data from 37 weather stations across the Tarim Basin during 1961-2010,the paper analyzed the vapor variation trend,period,abrupt changes and their causes.The results show that the increase trend of surface vapor content over the Tarim Basin mostly conforms with the average trend coefficient of 0.48.There were 3 centers displaying a trend of high vapor increase and 3 centers displaying a low vapor increase.These centers were distributed in strips and blocks across the basin from northeast to southwest.Notable inter-decadal variations in annual and seasonal vapor contents occurred in the Tarim Basin during the 50 years of the study period,with more vapor after the mid-1980s and less vapor in the 1960s and the 1970s.The significant increase in vapor content in the 50 year period occurred mostly in the 1980s and the 1990s.The increasing trend across the four seasons was strongest in summer,reaching 0.43,and weakest in spring.Great variations existed between the spring trend and the annual,summer,autumn and winter trends.During the 50-year study period,there are distinguishable periods of 4-6 years and 8-10 years in which the annual and seasonal vapor contents varied alternately between low and high concentrations.The annual vapor content and that of the four individual seasons all changed abruptly in about the mid-1980s (α＜0.05).The west wind circulation,Tibetan Plateau circulation and the annual mean temperatures of the Tarim Basin are the main factors that influenced the surface vapor content over the study area,of which the Tibetan Plateau circulation may be the most important one.