Abstract: The method for determination of arsenite (As (Ⅲ) ) , arsenate (As (Ⅴ) ) , methylarsonic acid (MMA) , dimethylarsinic acid (DMA) , and arsenic betaine (As B) arsenic species in Lentinus edodes and culture medium by HPLC-ICPMS has been developed.Samples were extracted with ultrasonic instrument in 70 ℃, then separated by HPLC on an anion chromatography and quantification by ICP-MS.Good linearities of 5 arsenic species were observed with correlation coefficients above 0.9999, the linear range was 0 ~ 100.0 ng/m L.Recoveries were between 81.0% and 108.9% and the relative standard deviation were within 1.6% ~6.3% (n = 6) .With the actual samples tested the As (V) was the main species in culture medium.The content had little relation with its cultivation time.It had more content As (Ⅲ) , As (Ⅴ) and As B in Lentinus edodes.Although the total arsenic results conform to the requirements of the national standards, but high toxic inorganic arsenic are majority.