Abstract: Clarifying the spatial and temporal variation of vapor pressure deficit (VPD) can help to investigate the response of air dryness to climate change. Based on the meteorological observation data of 105 stations in southwest China and empirical formula of VPD, this study used Mann-Kendall test to analyze the abrupt shift of VPD during 1982-2015. According to the partial correlation analysis, we discussed the temporal variation in VPD before and after the breakpoint year, and further to identify the climate factors which affect the trend of VPD. The results showed that the year 2000 was the breakpoint for the temporal variation in VPD for the period of 1982-2015. VPD change trends abruptly increased from 0.001 kPa/a to 0.005 kPa/a, and more and more stations showed increasing trend of VPD after 2000. This phenomenon indicated that area of southwest China has shown a drier air stress after 2000 since the relative humidity decreased more than that before 2000. Further study on the abrupt change in progress of VPD showed that, although the increasing external water vapor flux and actual evapotranspiration after 2000 may bring more water into air (namely, increasing actual vapor pressure), the rapidly rising temperature induced more water holding capacity in air, and thereby resulting in enhancing VPD increasing trends. This study suggests that higher temperature after 2000 indirectly affecting VPD via disproportionally increasing saturated vapor pressure played a more dominant role. This study is helpful in deep understanding of the climate change and revealing the relevant mechanisms behind the change of VPD. The results of this study would provide scientific support for ecosystem construction and climate change adaptation for southwest China.