The invention discloses a method for degrading atrazine in a water body through activating peroxymonosulfate by using potassium ferrate. The invention relates to the water treatment method and solvesthe problem of low activation efficiency of single peroxymonosulfate. The method comprises the following steps that a ferrate and a peroxymonosulfate are added in a polluted water body, sulfate free radicals and hydroxyl free radicals with a strong oxidizing property are generated with the utilization of mutual interaction of the ferrate and the peroxymonosulfate, and refractory organic pollutantsof organic wastewater are further oxidized, so that the purpose of degrading organic pollutants is achieved. The method provided by the invention has efficient and quick operation and simple operation at normal temperature; the leaching rate of iron ions in a using process is very low; secondary pollution is reduced; and the method is adapted to extensive pH conditions, and has a wide applicationprospect in the purification of organic polluted water bodies.