Abstract: Reed is perennial wetland vegetation, whose root has the ability to release oxygen and oxidants into the rhizosphere, and form iron oxides at the root surface or rhizosphere. According to the amphoteric colloid ability of reed root biogenic iron oxides, the iron oxides were used as adsorbing material obtained by the methods of both direct obtaining and high temperature carbonization, the adsorption effect of this material to pentavalent arsenic [As (V)] was studied by isotherm method. The results showed that the As (V) adsorption ability of iron oxides under acidic condition was significantly higher than that in neutral or alkaline condition. The adsorption content increased with the increase of As concentration in the external medium solution, when the As concentration was 200 mg/L, the adsorption content of two iron oxides treatments reached (17.00±3.25) and (12.82±1.01) mg/g, respectively. The adsorption of As by iron oxides could be well described by Langmuir and Freundlich isothermal adsorption model. The maximum adsorption amounts of As obtained by Langmuir isotherm equation were (17.72±1.09) and (21.94±6.74) mg/g, respectively. Therefore, the biogenic iron oxides had strong absorption ability to As (V). Overall consideration of the adsorption ability and the feasibility of polluted water management, iron oxides treated by high temperature carbonization were better than that of direct obtaining.