The changes of total arsenic and different arsenic species in Porphyra yezoensis collected from January to April in 2011 from three coastal areas in Jiangsu Province were determined and the characteristics of As accumulation were for the first time analyzed.Results showed that in all samples collected from different areas and times,the organic arsenosugar(AsS)accounted for 90.40%-98.14% of the total As,the second high content was dimethyl arsenic(DMA)and the lowest was inorganic arsenic(iAs),which ranged from 0.054 mg/kg to 0.14 mg/kg.And there are significant differences in three arsenic species(P<0.05).In addition,the total arsenic and arsenosugar in P.yezoensis peaked in February and then decreased gradually,while the content of iAs and the percentage of iAs to total arsenic kept decreasing from January to April in all the samples collected from three coastal areas.P.yezoensis had high As accumulation capability as the bioconcentration factor(BCF)was from 454.4 to 623.8.Present study further proved that the iAs content in P.yezoensis is far below the maximum limit according to the legislation in our country.