Abstract: Under global climate change and intensifying human activities, estuarine and coastal ecosystems are facing multiple environmental challenges, including eutrophication, hypoxia, and acidification, making them a frontier focus in current marine environmental research. This paper systematically reviews the driving mechanisms underlying low oxygen and acidification, focusing on key processes such as nutrient enrichment, water-column stratification, organic matter sedimentation, and microbial remineralization. It further summarizes the response characteristics of coastal community structures under coupled hypoxia-acidification conditions and their impacts on biogeochemical cycles. The results indicate that nutrient loading stimulates primary production, which in turn enhances organic matter deposition and microbial remineralization, leading to declines in bottom-water dissolved oxygen and pH. The coupled hypoxia-acidification phenomenon is further amplified by water-column stratification and reduced hydrodynamic exchange and is typified by multi-process interactions, pronounced spatiotemporal heterogeneity, nonlinear responses, and temporal lags. Ultimately, these changes tend to simplify food-web structure and increase the risk of greenhouse gas emissions, such as N₂O. By examining case studies from typical regions including the Yangtze River Estuary, Pearl River Estuary, Chesapeake Bay, and the Baltic Sea, this study further analyzes the differences among various marine units in terms of nutrient sources, runoff and tidal intensity, and carbonate buffering capacity, as well as their regulatory roles in the formation of localized hypoxia and acidification. Additionally, the study summarizes the major issues and challenges currently facing nearshore ecological management, including cross-regional coordination, mismatches in management scales, and delays in ecological restoration, and proposes an integrated "watershed-estuary-coastal" management framework. This approach emphasizes enhanced land-sea integration and regional collaboration, improves regulation of ecological processes, and strengthens long-term monitoring systems to enhance the resilience and safety of coastal ecosystems, thereby providing scientific support for sustainable coastal environmental management.