Abstract: The seedling growth of maize was studied by the method of Indoor potted plants, and the seedling corn clover growth index(Plant height, root length ,stem thick ,fibrous root number, fresh weight ), root activity and leaf protection enzyme was determined by seedling treatment with thiacloprid with 2 a.i g/kg,4 a.i g/kg,5 a.i g/kg,6 a.i g/kg and 8 a.i g/kg(seed).The results showed that the seed treatment of thiacloprid could significantly increase the corn seeding’s growth, leaf protective enzyme and root vigor, and all of them increased first and then decreased with the increase of the effective components of thiacloprid, and the optimum seed dressing was greater than that of imidacloprid. And the treatment of 8.0 g / kg had a slight inhibitory effect on the growth of maize plants, but the leaf protective enzyme and root vigor were still higher than the control treatment. The results suggest that the appropriate dose of thiophanate corn seed dressing can significantly promote the growth of corn seedlings, as well as improve the activity of protective enzyme and root vigor.