To establish a method for measuring methylmercury and other mercury species in aquatic products by HPLC-AFS. MethodsThe samples were extracted and centrifuged after hydrochloric acid ultrasoundtreatment. 5% of Acetonitrile, 4.62g/L ammonium acetate and 1.2g/L cysteine solution was used as mobile phase. Then the samples, being tested with AFS after C₁₈ seperated, were quantitatively determined by external standard method. There was no need of oxidization or ltraviolet photolysis. ResultsThe best linear range of methylmercury, ethylmercury and inorganic mercury was 0-50μg/L with correlation coefficients above 0.9990, the detection limit was 0.5-1.5μg/L, the precision relative standard deviation was less than 6%, and recovery of spiked samples was 78%-120%. Methylmercury measurement of standard substance in fish was within the reference range.ConclusionThis method was simple, sensitive, accurate and suitable for the determination of mercury species in aquatic products.