Abstract: OBJECTIVE To develop a method to determine four arsenic(As) speciation including arseniteAs(Ⅲ), arsenateAs(V), monomethylarsine(MMA), dimethyarsine(DMA) by HPLC-AFS using ultrasound and enzymatic hydrolysis in animal derived traditional Chinese medicines. METHODS Add pepsin to the samples after ultrasound and enzymatichydrolysis (pH 2.5) with 55℃ for 20 min, centrifuged at 6 000 r·min^-1 for 3 min. Took the supernatant, filter the sample. The sample was separated on an Hamilton PPRP-X100 anion exchange column(150 mm×4.6 mm, 5 μm) with the mobile phase of 1 mmol·L^-1 NH₄H₂PO₄(pH 8.5) and 20 mmol·L^-1 NH₄H₂PO₄(pH 7.0) by the gradient elution. The flow rate was 1.0 mL·min^-1 and the injection volume was 100 μL. RESULTS The separation was achieved within 13 min for four arsenic speciations. The detect limits were 0.01, 0.01, 0.01 and 0.02 mg·kg^-1 for MMA, DMA, As(Ⅲ) and As(V) respectively. The recoveries of four arsenic speciations ranged from 93.4% to 105.4%, the RSDs of precision were among 0.8% to 4.4% with the spiked amounts of 0.03-0.1 mg·kg^-1 in the samples. CONCLUSION The developed HPLC-AFS method using ultrasound and enzymatic hydrolysis for determination of As speciation has the advantages of simplicity, high extraction rate, good precision and high accuracy.