Abstract: The chemical constituents from the ethanol extract of Ceriops tagal were isolated and purified by column chromatography on silica gel,Sephadex LH-20 and HPLC. Their structures were identified by physical and spectral data. Ten diterpenoids were isolated and elucidated as (5S*,8S*,9S*,10R*,13S*)-2,16-dihydroxydolabr-4R*,18-epoxy-3,15-dione (1)、tagalsin B (2)、ent-5α,2-oxodolabr-3-ene-3,15,16-triol (3)、(5S*,8S*,9S*,10R*)-3,13S*-dihydroxy-15,16-dinorlabr-3-en-2-one (4)、(5S*,8S*,9S*,10R*,13S*)-3-hydroxy-16-nor-2-oxodolar-3-ene-15-oic acid (5)、(5S*,8S*,9S*,10R*)-13S*,18-dihydroxy-15,16-dinordolabr-4(18)-ene-3-one (6)、(5S*,8S*,9S*,10R*,13S*)-18-hydroxy-16-nor-3-oxodolabr-4(18)-en-15-oic acid (7)、(5S*,8S*,9S*,10R*)-13S*-hydroxy-4S*,18-epoxy-15,16-dinordolabr-1-en-3-one (8)、ent-8(14)-pimarane-16,18-dihydroxy-15-one (9)、ent-8(14)-pimarane-15,18-diol (10). Additionally,compound 1 was a new compound,and compounds 3 and 5 were obtained from C. tagal for the first time．

Key words: mangrove, Ceriops tagal(Perr.) C. B. Robinson, dolabrane-type diterpenoids, pimarane-type diterpenoids