Abstract: After 1.000 0 g of the sample was ultrasonically extracted with 38 mL of a mixed solution (pH 8.5) of 0.5 mmol·L^-1 (NH₄)₂CO₃ solution and methanol (99+1) for 2 h, 2 mL of acetic acid was added into the extract and the solution was diluted to 50 mL with water. After centrifugation, the supernatant was seperated on a Hamilton PRP-X100 anion analytical column (250 mm×4 mm, 10 μm), with a mixture (pH 8.5) of 0.5 mmol·L^-1 (NH₄)₂CO₃ solution and methanol (99+1) as mobile phase A, and a mixture (pH 8.5) of 50 mmol·L^-1 (NH₄)₂CO₃ solution and methanol (99+1) as mobile phase B, for gradient elution. Nine arsenic species were separated within 20 mins and detemined by ICP-MS. Linear relationships were found between the peak areas and the mass concentrations of nine arsenic species in definite ranges, with lower limits of determination (10S/N) in the range of 50-100 μg·kg^-1. Recovery obtained by standard addition method were in the range of 74.0%-109%, and RSDs (n=6) were in the range of 5.4%-13%. The proposed method was used to analyze marine products and it was found that the main arsenic specie in the sample was non-toxic arsenic betaine.