The invention relates to a beta-type-hydroxyl-ferric-oxide-loaded natural-cellulose-modified functional material and a preparing method and application thereof, and belongs to the technical field of industrial wastewater treatment.The preparing method of the material includes the steps of preparing natural cellulose, modifying the natural cellulose and loading beta-type hydroxyl ferric oxide.The prepared functional material has more adsorption point locations and multiple adsorption performances, other ions and salt in water can be adsorbed, and the problem of strong brine treatment generated during deep treatment of arsenious wastewater at present is solved.The functional material is high in adsorption capability, the concentration of discharged treated arsenious wastewater is lower than 0.05 mg/L, selective desorption can be carried out according to different adsorption modes, and the function material is easy to degrade, free of environmental toxicity and easy to apply and popularize.