Water retention is one of the essential ecosystem service functions, playing a critical role in maintaining regional ecological security and the sustainable development of water resources. This study, based on the principle of water balance and employing the optimal parameters-based geographical detector, revealed the spatiotemporal patterns of global water retention from 1991 to 2019, identified the main driving factors, and proposed a method for assessing water retention potential. The results indicate that tropical regions represent the core zones of global water retention, whereas arid and semi-arid areas exhibit pronounced declining trends in water retention. Autumn and winter represent the peak periods of retention, while spring and summer correspond to risk periods. Precipitation is the primary factor influencing the spatial variability of water retention, and it exhibits a significant nonlinear-enhance interaction with evapotranspiration, jointly shaping the spatial pattern of water retention. Globally, the potential for increasing water retention is predominantly at medium to high levels, with most regions having room for enhancement, and South America showing the greatest potential. This study provides a critical theoretical foundation and data support for the scientific enhancement of water retention in the future and offers valuable reference for the formulation of sustainable water resource management and ecological conservation policies.