<p>Mangrove wetlands are a vital component of the blue carbon ecosystem, which is of great significance to coastal ecosystems and the global carbon balance. However, mangrove forests worldwide face a combination of natural and anthropogenic threats. This study employs high-resolution sedimentology, geochemistry, and pollen analysis to reveal the sedimentary evolution and vegetation succession in the mangrove wetland of Dongzhai Harbor, Hainan Island. By utilizing multiple proxies, including ¹⁴C chronology, δ¹³C, C/N, and the chemical index of alteration (CIA), we identified three distinct stages in the sedimentary records spanning from the Late Pleistocene to the modern age. Prior to the last glaciation, during the Late Pleistocene, the study area exhibited marine carbonate facies, with an abundance of marine-derived organic matter. During the low sea-level stage of the last glaciation, the strata in the core location were exposed. Following the last glaciation, the study area gradually transitioned into intertidal settings in response to fluctuating sea levels. Since the Middle Holocene or even earlier, sedimentary organic matter continued to accumulate as terrestrial C3 vegetation and mangrove forests established, persisted, and developed. This period witnessed the formation of the current estuarine environment. Simultaneously, the pioneering mangrove species, probably represented by <i>Avicennia</i>, might be initially established, followed by <i>Rhizophora, Bruguiera</i> and <i>Ceriops</i> communities, ultimately being replaced by <i>Kandelia obovata</i> to date. These findings not only fill the gap in the study of paleo-mangroves in China but also contribute valuable knowledge to the global reconstruction of paleo-mangroves, providing crucial reference for the conservation of mangroves and prediction of their responses in the context of climate change.</p>