The invention relates to safety herbicide for a corn field. An active ingredient of the safety herbicide is prepared by mixing topramezone and one or more than one of atrazine, ametryn, amides active compound, the mass ratio of topramezone to atrazine is 0.5-8:1-30, the mass ratio of topramezone to ametryn is 0.5-8:1-30, and the mass ratio of topramezone to amides active compound is 0.5-8:1-30. The amides active compound is alachlor, pretilachlor, butachlor or metolachlor. The topramezone has remarkable synergistic effect after adding atrazine / ametryn, the herbicide has good prevention and control effect on weeds and has good preventing and removing effect on malice broad leaf weeds such as cirsium setosum, chicory, acalypha australis and dayflower. The topramezone has a wide weed control spectrum, is safe for the height of corns, and can effectively synergize after combining the atrazine and the like. After combination, use amount of atrazine alone is reduced, and safety of the corns is improved.