The climate features of atmospheric water vapor in Yangtze River Delta region are analyzed by use of 7 years′ Precipitable Water Vapor(PWV) data observed by GPS observational Network, and the relations between climate characteristics of Atmospheric Precipitable Water vapor and heavy rain in Meiyu season are also studied. The results show that: PWV distribution in the Yangtze River Delta region are the higher the north and higher the west, the average PWV during summer months are higher than that of the winter months about 20mm, and the PWV gradient from south to north is clearly higher than that from west to east, which shows that moisture transportedto Yangtze River Delta region by northern flow is important. PWV in Yangtze River Delta region has a significant seasonal change, the maximum PWV are found in August in summer, and the minimum PWV occurred in January in winter, and the PWV changes in spring and autumn are strong than that in summer and winter; while the PWV in Yangtze River Delta region has no significant cyclical changes in year and in day. In addition, there is obvious correlation between PWV and severeprecipitation duringMeiyu Period, when the PWV value quickly increase from the low-value to more than 60 mm, or PWV values remained at high values after severeprecipitation, severeprecipitation often occurs, which maybe provides a new signal for us to forecasts heavy rain in the Yangtze River Delta.