Metolachlor was chosen in this experiment to control weeds in zucchini field.The results showed that metolachlor was safe to zucchini,and the dosage was 1080 g/hm²,and it was 1476 g/hm² when there were many granineous weeds.It can be applied after sowing but before seedling emergence.It could control barnyard grass,lambs quarters,redroot amaranth,but it could not control common cirsium,Japanese hop Piemarker.Zucchini yield increased by 4.7-15.7% compared with manual weed controlling.