Composite metal oxides generated by in-situ reactions are introduced into arsenic-containing raw water, and the electronegative As (III) in the water that is difficult to remove is converted into electronegative As (V) that is easy to remove through the interfacial oxidation of the composite metal oxides. The adsorption effect of the composite metal oxides is used to adsorb As (V) in the water to form particulate arsenic; further, the particulate arsenic is filtered and removed in subsequent contact filtration units. During long-term operation, a composite oxide filter membrane will gradually form on the surface of the filter media, and in actual engineering operation, the thickness of the filter membrane will gradually increase to form another barrier for arsenic removal. Key technical contents include: in-situ preparation technology of composite metal oxides; oxidation-adsorption arsenic removal technology of composite metal oxides and adsorption-contact filtration arsenic removal technology. The Dongzhou Water Plant of Zhengzhou Water Investment Holding Co., Ltd. has a water supply scale of 200,000 tons/day. After adopting this technology to enhance arsenic removal in the water plant, the arsenic removal rate has increased by about 30%, and the arsenic concentration in the factory water has stably reached the standard (at about 7μg/L), the turbidity removal rate has increased by 0.5% to 5.0%, and the iron and manganese content in the effluent fully meets the requirements of national standards; the anti-impact load capacity of the filter has been significantly improved; the new water purification cost is 0.02~0.04 yuan/ton. The composite metal oxide adsorption-contact filtration enhanced arsenic removal technology gives full play to the process function of a water-dropping aeration-contact filtration iron and manganese removal water plant. It achieves enhanced arsenic removal based on the existing process of the water plant, and has good technical feasibility and economic feasibility.