The South China Sea is one of the mangrove hotspots in the world. The eastern coast of Guangdong Province is located at the northernmost boundary of the South China Sea and is characterized by the marginal mangrove floristic composition and communities. Using satellite imagery interpretation, 23 sites were chosen and surveyed. A total of 12 species of true mangrove, six species of semi-mangrove, and seven species of associated plants were recorded in the surveyed sites. The main forms of mangrove communities were shrubs and dwarf trees with the average height of 1.50 to 8.60 m. The Shannon-Wiener index ranged from 0.533 to 1.239, while the evenness index varied from 0.662 to 0.957. There was no significant correlation in these indices between natural forests and plantations. The mangrove communities were classified into four types: pioneer plantation, pioneer natural forest, medium natural forest, and climax natural forest. The environmental factors between forest stands differed significantly, and total organic carbon, salinity, and total nitrogen in sediments were highly correlated with community distribution. Although plant species abundance increased from 20 to 24 species compared to the data obtained in 1985, reduction in some associated plants and retreated semi-mangrove populations indicated that the mangrove in eastern Guangdong were facing tremendous environmental pressure. Species diversity and evenness in the mangrove in eastern Guangdong were lower than those of mature mangroves. Reclamation in the past several decades contributed to natural mangrove decrease and habitat fragmentation. Given the current state of mangrove vegetation, improvement in plantations and residual secondary natural forests is the focus of mangrove restoration in key areas, including Futian in Shenzhen Bay, Xiezhou in Fanhe Harbour, and Liuhewei in Hanjiang Estuary.