Intertidal foraminifera was widely used in paleoenvironmental changes, for example, high-resolution relative sea-level researches, however, this kind of research is scarce in South China coast. A 300-cm in length core was selected in upper intertidal zone of mangrove in Qi’ao Island, Pearl River estuary, and AMS¹⁴C dating, foraminifera, grain size and grayscale analysis have been done for the sediment. The result show that below the depth of 180 cm, the sediment are homogeneous gray clayey silt, containing abundant calcareous foraminiferal tests. The assemblage are dominated by Ammonia spp. (78.7%), with common species Proelphidium granosum (6.6%) and Elphidiella kiangsuensis (5.6%), indicating a subtidal or mudflats environment; Above the depth of 180 cm the sediment are yellowish gray clayey silt with abundant plants debris and residues, containing agglutinated foraminiferal tests. The assemblage are dominated by Arenoparella mexicana (50.6%) with common species Miliammina fusca (17.5%), Trochammia sp. (6.8%), indicating an upper or middle intertidal mangrove environment. Based on the AMS¹⁴C dates, the core recorded a sedimentary history from ~4300 cal a BP, the study area evolved from mudflats to mangrove at ~2400 cal a BP, resulted from the decrease of relative sea-level due to deltaic progradation. However, there are two fine grain size sediment containting calcareous foraminiferal tests in mangrove sediment, corresponding to 1022 - 729 cal a BP and 508 – 358 cal a BP, probably related to sub-regional sea-level rise. The grayscale suggested three phase with high content of organic matter, corresponding to ~3000-2700 cal a BP, 1200-1100 cal a BP, 600-500 cal a BP, indicating warm and humid climate, this time is very close to the period of sea-level rise.