By means of the atmospheric precipitable water vapor data measured by groundbased GPS at Shijiazhuang and Zhangjiakou, a comparison is made between the radiosondecalculated and the GPSretrieved precipitable water. A severe precipitation case occurred in the southern Hebei Province in July 2007 is analyzed. It is found out that the GPS retrieval of precipitable water, which is slightly greater than the radiosondederived, is more reliable and useful; the results of the two methods have accordant variation trends. For the single station, there exist certain limitations in the effective radius of the GPSretrieved perceptible water.