Rare actinomycetes are potential resources of screening novel natural products, and have already gained extensive attention worldwide.Mangrove forest is a special ecosystem along the intertidal zone harboring abundant microbial diversity.In this study, we exploited the diversity of actinomycetes by culture-independent method (454-pyrosequencing) and the diversity of culture-dependent rare actinomycetes by traditional culture-based method of four sampling sites (intertidal zone,Xylocarpusmekongensis, bruguierasexangula and land) in the soil of Bamen Bay mangrove forest of Hainan province.The culture-independent result revealed that the microbial community in mangrove soil was significantly diverse.12 groups at order level (Frankiales, Corynebacteriales, Micromonosporales,Propionibacteriales and Pseudonocardiales accounted for over 80% of total number) and 25 groups at family level(Acidothermaceae, Micromonosporaceae, Mycobacteriaceae, Nocardioidaceae,Pseudonocardiaceae, Streptomycetaceae, Frankiaceae, Propionibacteriaceae, Microbacteriaceae and Kineosporiaceae made up over 80% of total amount) were detected in this sequencing.The diversity index and the relative abundance of actinomycetes were distinct among sampling sites, but similar diversity existed in two types of mangroves except for Elev-16S-976 group was only detected in Xylocarpusmekongensis.Other groups in the two mangrove samples revealed similar abundance with slight differences.Frankiales took up a major proportion in the total actinomycetes amount (34.9% in average)and especially been predominant in the Land sample (49.8%).Micromonosporale ranked third in total amount (13.4% in average), and took the first position in the proportion of rare actinomycetes and hold larger percentage in mangrove habitats (17.5% in average) than which in the other two samples (9.3% in average).By the cultivation method, five pre-treatment methods and five media with antibiotics were utilized to isolate rare actinomycetes from the corresponding samples above.150 actinomycete isolates possessing rare-actinomycete morphologies were selected and preliminarily identified by 16S rDNA sequencing.Isolates were preliminarily identified into 8 families (Micromonosporaceae,Pseudonocardiaceae, Streptosporangiaceae, Nocardiopsaceae, Tsukamurellaceae, Thermomonospraceae,Geodermatophilaceae and Nocardiaceae) and 13 genera (Actinomadura, Blastococcus, Rhodococcus,Nonomuraea, Microbiospora, Streptosporangium, saccharopolyspora, Pseudonocardia, Tsukamurella,Nocardiopsis,Micromonospora, Jishengella and Verrucosispora.).Generally, the phylogenetic diversity of cultured rare actinomycetes was accorded with the 454-pyrosequencing result: all ofthe rare actinomycetes family groups separated by traditional method could be revealed by pyrosequencing although some of them were just detected in small amount.However, some genera incubated were failed to be detected by pyrosequencing.