Abstract: Sensibility of 18 maize cultivars to acetochlor in seedling stage and the changes of sensibility of Nongda 108 cultivar in different seedling stage was studied by pot cultivation method. The results showed that sensibility of maize to acetochlor was different among the cultivars, and the sensibility of chit was different from root . The regression analysis showed that the weight inhibiting of chit and root had linear relation with the log of the acetochlor dosages. The inhibiting regression equation and LC 50 of chit and root weight were gained by the method of Finney. The sequence of sensibility expressed by chit fresh weight inhibition rate as follows: Yedan13>Yedan12>Lunuo6>Yedan22>Denghai1>Ludan981>Yedan4>Xiyu3>478>Nongda 108>Luyu16>Huang C>Qi319>Luyu10>H21>Ludan50>Luyuandan14>Ludan92. The sequence of sensibility expressed by root fresh weight inhibition rate as follows: Qi319>478>Lunuo6> Denghai1 >H21>Huang C>Ludan981>Ludan92>Yedan12>Yedan22>Yedan4>Xiyu3>Luyu16> Ludan50 >Luyu10>Nongda108>Yedan13>Luyuandan14. In seeding stage of Nongda 108, the earlier contacted with acetochlor, the more growth of maize reduced was. And the chit of Nongda 108 was more sensibility to acetochlor than the root.