A treatment unit packed by granular adsorbent of Fe-Mn binary oxide incorporated into diatomite (FMBO(1:1)-diatomite) was studied to remove arsenic from anaerobic groundwater without any pre-treatment or post-treatment. The raw anaerobic groundwater containing 35-45 μg/L of arsenic was collected from suburb of Beijing. Arsenic(III) constituted roughly 60%-80% of the total arsenic content. Approximately 7,000 bed volumes (ratio of efluent volume to adsorbent volume) treated water with arsenic concentration below 10 μg/L were produced in the operation period of four months. The regeneration of FMBO(1:1)-diatomite had been operated for 15 times. In the first stage, the regeneration process significantly improved the adsorption capacity of FMBO(1:1)-diatomite. With increased loading amount of Fe-Mn binary oxide, the adsorption capacity for arsenic decreased 20%-40%. Iron and manganese in anaerobic groundwater were oxidized and adsorptive filtrated by FMBO(1:1)-diatomite efficiently. The final concentrations of iron and manganese in efluents were nearly zero. The continued safe performance of the treatment units proved that adsorbent FMBO(1:1)-diatomite had high oxidation ability and exhibited strong adsorptive filtration. A treatment unit packed by granular adsorbent of Fe-Mn binary oxide incorporated into diatomite (FMBO (1: 1) -diatomite) was studied to remove arsenic from anaerobic groundwater without any pre-treatment or post-treatment. The raw anaerobic groundwater containing 35 Arsenic (III) roughly 60% -80% of the total arsenic content. Approximately 7,000 bed volumes (ratio of efluent volume to adsorbent volume) treated water with arsenic concentration below -45 μg / L of arsenic was collected from suburb of Beijing. The regeneration of FMBO (1: 1) -diatomite had been operated for 15 times. In the first stage, the regeneration process significantly improved the adsorption capacity of FMBO (1: 1) 1) -diatomite. With increased loading amount of Fe-Mn binary oxide, the adsorption capacity for arsenic decreased 20% -40%. Iron and manganese in anaerobic groundwater were oxidized and adsorptive filtrated by FMBO (1: 1) -diatomite efficiently. The final concentrations of iron and manganese in efluents were nearly zero. The continued safe performance of the treatment units proved that adsorbent FMBO (1: 1) -diatomite had high oxidation ability and strong binding adsorptive filtration.