To further understand the detailed characteristics of atmospheric water vapor over Hunan Province , the retrieved precipitable water vapor (PWV) by 72 ground GNSS stations in Hunan from 2016 to 2020 is used to analyze the spatial-temporal and geographical distribution characteristics in this paper. The results indicate that the GNSS/PWV in Hunan is very close to the PWV obtained from the radiosonde , and can be used for the analysis of atmospheric water vapor characteristics in Hunan Province . The atmospheric water vapor in Hunan gradually decreases from south to north overall . With a significant influence of altitude the low-value areas of water vapor are predominantly found in the higher-altitude mountain regions . The atmospheric water vapor in Hunan shows obvious characteristics of zonal and vertical distribution , negatively correlated with the altitudes and latitudes of stations with correlation coefficients being - 0 . 5170 and - 0 . 3063 respectively , both having passed the significance test at a level of 0 . 01 . The monthly variation of atmospheric water vapor follows a pattern of single peak , with the highest values occurring in July and August , and the lowest values in January and February. Influenced by topography and monsoon , the seasonal distribution features show that water vapor resources are abundant in summer , significantly reduced in spring and autumn , and relatively scarce in winter. These results can serve as an important reference for heavy precipitation monitoring and early warning , cloud water resource development , and weather modification operations in Hunan Province .