Salt lakes represent critical nodes in global hydrological and biogeochemical cycles, accounting for approximately 44% of the total lake water volume worldwide. Water salinity, as a key variable regulating physical, ecological, and chemical processes in salt lakes, plays a decisive role in regional ecological security and the sustainability of water resources. This study presents an interdisciplinary review of the progress in the research topic on the pattern and changes of salt lake water salinity. With the growing prominence of ecological concerns, research on the water salinity of salt lakes has evolved from traditional hydrogeochemical descriptions to an interdisciplinary frontier that integrates the impacts of climate change, ecosystem responses, and remote sensing monitoring. The core driving force behind this transformation stems from the innovation of monitoring technology, that is, from traditional point sampling to a large-scale, long-term dynamic monitoring system centered on satellite remote sensing and machine learning. Synthesized analyses of global records reveal that global salt lakes are predominantly distributed across arid and semi-arid zones in both hemispheres, with the Tibetan Plateau (TP) exhibiting the highest density and heterogeneity of water salinity. Over the past few decades, the changes in water salinity of the global large salt lakes display a significant spatially heterogeneous pattern. Salt lakes in arid regions frequently undergo aggravated salinization driven by agricultural irrigation and aridity, whereas high-altitude salt lakes, particularly on the TP, exhibit a desalination due to increased water volume and glacial melt associated with warming and wetting climate. These changes in salt lake water salinity dynamically reshape food web structures, regulate physical stratification and elemental cycling, and ultimately exert cascading impacts on soil salinization, drinking water safety, and infrastructure across watersheds. Future efforts should focus on integrating multi-source observations from next-generation satellites with hybrid models, to move beyond mere monitoring toward a predictive understanding of water salinity change, allowing us to quantitatively attribute its drivers and forecast its cascading impacts across interconnected socio-ecological systems, from the stability of aquatic food webs and soil health to the long-term resilience of regional water security and critical infrastructure.