The changes in the upper-air specific humidity during 1958-2005 were studied based on time series of homogenized radiosonde dewpoint data from 92 selected stations in China. The data suggest that in the vertical direction more than 90% of water vapor is concentrated in the lower and middle troposphere, and the horizontal structure shows zonal distribution decreasing with latitude. Temporal analysis of the annual specific humidity time series by using the moving average and accumulation anomalies shows decadal variability in the lower and middle troposphere with negative anomalies from late 1960s to early 1980s and positive anomalies after the late 1980s. The linear trend of the average specific humidity in China is positive in the lower troposphere and negative above the mid-troposphere for 1958-2005. During 1979-2005, a positive trend in the lower troposphere and a negative trend in the lower stratosphere were both prominent. Time series of temperature and specific humidity in the troposphere and lower stratosphere simultaneously changed during 1958-2005; furthermore, their correlations at all levels are statistically significant, which suggests that temperature strongly affects the specific humidity changes. The spatial distribution of the linear trend suggests that the specific humidity in the lower troposphere increase in most stations during 1958-2005 and the increasing trends are more obvious after 1979. In the mid-troposphere, negative trends are in the regions south of the Yangtze River and positive trends are in the rest of China. The analysis of the vertical profiles of the linear trends in five subregions of China shows that the highest positive trends are over Northwest China and slightly positive trends are over the regions south of the Yangtze River in the lower and middle troposphere. During 1958-2005, the trends of seasonal specific humidity in the lower troposphere exhibit obvious differences with a wetting trend in the summer and winter, and a drying trend in spring and autumn. In contrast, during 1979-2005, the specific humidity trends for all seasons are consistently positive, and the wetting trend in the summer is more prominent in the lower and middle troposphere.