Abstract: In order to protect agricultural ecological environment and optimize the dosage of herbicides, 40% cyanamide acetochlor herbicide was used in this experiment to set up three different doses for treatment, in order to obtain the ideal effective dose for reduction. The results showed that 40% cyanamide acetochlor herbicide was reduced by 15% on the basis of conventional dosage, which had the stone effect as the conventional dosage, the emergence rate was 91.53%, the control efficiency which the number of weeds and fresh weight of weeds were 91.98% and 91.45.%, respectively,and the yield was at 9 623.72 kg/hm^2. Therefore, in order to achieve better ecological and economic benefits in maize production in southeastern Shanxi, this herbicide can be used up to 15%.