Abstract: DNAs from 7 txax of mangroves in Rhizophoraceae were extracted by using the CTAB method. A 260 /A 280 ratio of DNA solutions ranged from 1.6 to 2.0,and the length of DNA fragment was about 23kb. RAPD markers were used to assess the relationships among the 7 taxa of mangroves in Rhizophoraceae. Fifteen effective primers were screened from 30 10-oligonucleotide arbitrary primers,and a total of 617 DNA bands were amplified,among which 415(67.26%)were polymorphic. Based on UPGMA cluster analysis of 617 DNA bands amplified by the 15 primers,a DNA molecular dendrogram was established,which divided 7 species in Rhizophoraceae into 2 main groups. The average genetic distance among the 7 taxa was 0.41,and the maximum genetic distance was 0.56(0.6),which between Ceriops tagal and Bruguiera sexangula var. rhynchopetala. It indicated that the 7 taxa are in the same family. Group A included 3 taxa-Rhizophora apiculata,R.stylosa,Ceriops tagal;group B contained 4 species Bruguiera gymnorrhiza,B. sexangula,B. sexangula var. rhynchopetala,and Kandelia candel. The dendrogram obtained from the cluster analysis was consistent to morphological classification. A special DNA fragment,which named OPG05-900,was amplified to distinguish B. sexangula and B. sexangula var. rhynchopetala. The results could be valuable to the projects of plant introduction, ecological restoration and conservation in mangroves.