Abstract: The structure of real time system of monitoring water vapor derived from ground-based water is introduced. Its applications in meteorology are analyzed based on the precipitable water vapor derived from ground-based GPS. The time series of real time GPS-PWV is retrieved from observation data of being high spatial-temporal resolution,continuous,whole day and real time supplied by GPS networks. The application system of water vapor monitoring by ground-based GPS is constructed based on that. It supplies instruction for monitoring atrocious weather and short-time weather forecast,establishes the foundation for studying spatial-temporal distribution of atmospheric water vapor and exploiting atmospheric water resource through many disciplines.