Abstract: The residue and degradation of methomyl in brown rice, rice plants, soil and water of paddy fields were investigated using a gas chromatography-flame photometric detector (GC-FPD) method. As methomyl was applied at a range of concentrations from 0.045 to 0.450 mg/kg, average recoveries of 82.8%-91.0%, 84.4%-98.1%, 83.7%-90.3%, and 85.9%-86.9% were obtained in the brown rice, rice plants, soil and water samples with variations of 5.2%-8.1%, 6.8%-9.0%, 3.7%-7.7%, and 6.4%-8.3%, respectively. The degradation dynamics of methomyl in rice plants, soil and water were further investigated in four rice-planting regions, including Hunan, Hubei, Jiangxi and Zhejiang. The results showed that the half-lives of methomyl in rice plants in Hunan, Hubei, Jiangxi andZhejiang were 16.08, 4.47, 15.93， and 22.87 h, respectively. The half-lives of methomyl in paddy field waters were 6.74 h in Hunan, 3.88 h in Hubei, and 28.06 hin Jiangxi. Residues of methomyl in paddy field waters of Zhejiang, as well as in paddy field soils of the four tested regions were not detected. When methomylwas applied at double the recommended dose, its residue in brown rice, after 14d application, was lower than 0.5 mg/kg, the maximum residue limit required by Japan in its Positive List System for agricultural chemical residues in rice.