Abstract: The broad-leaved weeds in winter wheat could be effectively controlled when metsulfuron methyl was applied at the rate of 1.8～2.5g/hm2 in autumn in Beijing. The efficacy was higher than that by using tribenuron at the rate of 15g/hm2 in spring. The results of degradation in laboratory showed that when the initial metsulfuron-methyl dosage was under 6.25μg/kg, the residue was not harmful to succeeding crop maize after 215 days. A simple and fast bioassay technique was developed for sulfonylurea herbicides. Sunflower was an ideal material for bioassay. The minimum detectable concentration for metsulfuron-methyl with sunflower's root length was 0.125μg/kg. The optimal dosage response model is y=a+b lnx.