Abstract: The preliminary study of arsenic species in rat serum after oral administration of Niuhuang Jiedu tablet was established by high performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). With acetonitrile as extraction agent, water bath ultrasonic extraction at 60 ℃ was used as the pretreatment of serum samples. The extracting solution was separated by centrifugation at 13 000 r/min for 10 min, then filtered through 0.45 μm membrane. 20 mmol/L (NH₄)₂CO₃ (pH 9.7) and 3% methanol were used as mobile phase, and Dionex IonPac AS19 (250 mm×4 mm×10 μm) was used as analytical column for analysis of arsenic species in rat serum after oral administration of Niuhuang Jiedu tablet. Experimental results show that the detection limits of AsB, DMA(Ⅴ), As(Ⅲ), MMA(Ⅴ) and As(Ⅴ) are 0.05, 0.05, 0.08, 0.10 and 0.10 μg/L, respectively. The linear coefficients (R²) are more than 0.999, the recoveries are between 86.3% and 109.2% with the relative standard deviation less than 5%. The preliminary study found that DMA(Ⅴ) and U1 are the main arsenic species in rat serum after oral administration of Niuhuang Jiedu tablet, and a small amount of AsB and U2 are also detected in rat serum. The method is sensitive and high extraction efficiency, which can realize the simultaneous separation of various known and unknown arsenic forms, and provide technical support for the metabolic study of arsenic in rat blood.