Abstract: To explore the influence of 2,4-D butyl ester herbicide on the growth of millet, this study selected a few local cultivars to study the growing dynamics, biological yield, morphological indexes of millet after being sprayed with herbicide 2,4-D butyl ester. The results showed that starting from the 3-5 leaves, the herbicide was sprayed for 70 days. The herbicide had consistent influence on growing morphological indexes of different varieties of millet, the effect on root number, spike length and number of leaves was slight, while that on other indicators was somewhat greater. Investigation at different growth stages had different effects on growing morphology index. At seedling stage, the number of roots and plant height were greatly affected; at early stage of heading, dry weight, lateral root length, fresh weight and plant height were significantly affected; during mature period, fresh and dry weight, lateral root length, and plant height were heavily affected. The resistance on 2,4-butyl ester herbicides was different from different varieties at different times. Varieties for water land were sensitive while varieties for dry land was dull in a certain concentration of application. There was no difference between the two concentrations (750 mL/hm², 450 mL/hm²) on growth index at harvest period. The results showed that the growth of millet was delayed by the phytotoxicity of 2,4-D butylate ester, but the number did not change, the quantitative indicators were affected obviously, which indicated that biological production and the height of the plants decreased. So we should fully consider the input-output ratio and be careful with this herbicide.