Abstract: In order to confirm the control efficacy and safety of the soil-sealed herbicide 42% S-metolachlor·isoxaflutole·atrazine suspoemulsion against weeds in maize field under different doses, a field efficacy trial was designed using randomized block method. The results showed that it had good effects on the main weeds of maize field, including Echinochloa crusgalli（L.） P. Beauv., Chenopodium album L., Persicaria bungeana（Turcz.） Nakai ex T. Mori and Abutilon theophrasti Medikus when 42% S-metolachlor·isoxaflutole·atrazine suspoemulsion were used 1 890-2 205 g·ha^-1 by pre-emergence treatment. The plant control efficacy and fresh weight control efficacy on the total weed were 86.8%-95.0% and 88.9%-96.5% respectively. At 20 days, 40 days and tasseling stage after each dose treatment, there was no phytotoxicity to maize, and no effect on other non-target organisms. According to the results of yield measurement, the yield of each treatment was significantly increased compared with the blank control, and the incremental production rates was 74.4%-81.4%. The results indicated that the soil-sealing herbicide 42% S-metolachlor·isoxaflutole·atrazine suspoemulsion was safe to maize and had the good control effect on weeds. For the control of annual weeds in maize fields, the appropriate dosage is 4 500-5 250 mL·ha^-1(the effective component of 1 890—2 205 g·ha^-1).