40% Nicosulfurono2,4-D isooctyl ester is a new herbicide applied to corn field.Its controlling effect of weeds in corn field and its safety was studied in the experiment.The results showed that application of 40% Nicosulfurono2,4-D isooctyl ester at 600～720g.ai/ha at 3～6 leaf stage,its control effects of annual weeds 45 days after spraying was 86.2～99.2%.Corn output was not much different between it and manual control weeds.