The experiment was carried out in hand weeding maize land in Hainan Province 3 to 5 days after ridge cover.Acetochlor was applied and its weeding effect was studied.The results showed that applying acetochlor 3 to 5 days after ridge cover,namely,effective content 900 g/liter,preparations dosage 600 ml/hm2 plus water 450-600 liters/hm2,weeding effect was 100%.