Abstract: Almost all water vapor on Earth is concentrated in the troposphere, the content of it has a significant impact on global temperature, precipitation, and other meteorological factors, which can to some extent affect Earth’s climate change and regulate heat balance on a global scale. Tropospheric water vapor monitoring plays a crucial role in water resource management, extreme weather warning, and climate change research. In the process of continuous development and improvement of BDS/GNSS global satellite navigation technology, the retrieval of precipitable water vapor by BDS/GNSS has gradually become a new type of water vapor detection technology. Compared with traditional water vapor detection technology, BDS/GNSS can achieve high-precision and near real-time monitoring of water vapor. To deepen researchers’ understanding of BDS/GNSS precipitable water vapor (PWV), the paper provides a systematic review of the development process and research status of the retrieval of BDS/GNSS PWV, elucidating its inversion principles and methods. It mainly analyzes the application and development direction of ground-based BDS/GNSS water vapor monitoring in the field of water conservancy from high-precision water vapor monitoring, short-term and imminent rainfall forecasting, climate change, and drought & flood monitoring.