Abstract: Intertidal foraminifera has been widely used in paleoenvironmental reconstruction, and especially, in researches on high-resolution relative sea-level fluctuation. Unfortunately, such researches are lacking in the South China coast. This time, a long core up to 300 cm in length was retrieved from the upper intertidal zone of the mangrove on the Qi’ao Island of the Pearl River estuary. AMS¹⁴C dating, foraminifera, grain size distribution and grayscale analysis were employed to ascertain the possibility to apply the mangrove foraminifera as a high-resolution proxy for sea level fluctuation and paleoenvironmental evolution. Two foraminiferal assemblages were acquired from the core QA, a calcareous group dominated by Ammonia becсarii (78.7%), with common species Proelphidium granosum (6.6%) and Elphidiella kiangsuensis (5.6%), from a clayey slit sediment, indicating an estuarine subtidal environment; and an agglutinated assemblage dominated by Arenoparella mexicana (50.6%) with common species Miliammina fusca (17.5%), Trochammia sp. (6.8%), from a layer of sandy silt deposits with abundant plants debris and residues, indicating an upper or middle mangrove intertidal environment. AMS¹⁴C dates suggest that, the sediments formed approximately 4 200 cal. aBP, when the study area was a subtidal or mudflats environments. It turned to a middle-high mangrove at ～2 400 cal. aBP, resulted from the falling of relative sea-level caused by deltaic progradation. Two fine grained layers were intercalated in mangrove sediments, which contain calcareous foraminiferal tests corresponding to 1 022 ～ 729 cal. aBP and 508 ～ 358 cal. aBP respectively, probably related to a sub-regional sea-level rise. The grayscale suggests three phases of high humification, corresponding to ～3 000～2 700 cal. aBP, 1 200～1 100 cal. aBP, 600～500 cal. aBP respectively, indicating a warm and humid climate, which are close to the sea-level rise periods.