Study on biological characteristics of Heritiera lhtoralis populations showed that this population had a narrow colonization area of only 0. 7 hm^2. There were less than 1 500 individuals, and the number of individuals were decreasing continually. Though the population age structure was approximately pyramid-like, there were few young and middle-aged individuals, and the age structure of terrestrial subpopulation was reversed pyramid-like. The seed production of H. littoralis was low in nature, and so was the germination rate as well as the transformation rate from juvenile to adult. In addition, our laboratory experiments showed that removing shell of seeds was helpful to shorten the germination time but decreased the seedling survival rate of H. littoralis. The results show that the survival of H. littoralis population in Yanzao have been threatened seriously, and urgently needed to take effective actions to preserve the plants and habitats on site.