20% Nicosulfuron.Bromoxynil Octanoate is a new herbicide applied to corn field.It was cho-sen to control weeds in corn field and its safety was studied in this experiment.The results showed that appli-cation of 20% NBOSA at 270-300 g/hm²could control weed and it is safety.The optimum application time was 3-5 leaf stage.Control effects of annual monocotyledonous 45 days after application were 82.7%-89.0%,and control effects of dicotyledonous weeds were 77.7%-84.3%.The total control effects were 80.4%-86.8 %.Corn yield increased by 18.2% compared with manual weeding.