Abstract: Using the observed data of GPS water vapor in Tibet in July, 2008, the article studied the relationship between the total quantity of atmospheric water vapor and the relative humidity and the precipitation.The results indicated:1.Elevation influence is quite obvious, in ordinary, the total quantity of water vapor is low with high altitude.2.It is not a simple positive correlation between the total quantity of the water vapor and the real precipitation.3.The negative correlation between the mean daily temperature, the total quantity of water vapor in atmosphere and the relative humidity.