Abstract: A method based on QuEChERS sample preparation at weak alkali condition and ultra-performance liquid chromatography detection with hydrophilic chromatographic column was developed for determining pymetrozine residues in cotton and soil. The results indicated that average recoveries for cotton leaf at three levels (0.05, 0.1 and 0.5 mg/kg) ranged from 76.9%-91.1% with relative standard deviations (RSD) of 7.2%-8.2%, for cotton seed ranged from 76.4%-93.7% with RSD of 6.2%-9.8%. Average recoveries for soil at four levels (0.02, 0.05, 0.1 and 0.5 mg/kg) ranged from 83.8%-94.6% with RSD of 5.3%-8.0%. 10% pymetrozine·lambda-cyhalothrin suspending agent was applied in Shandong and Henan according to recommended dose (active ingredient 30 g/ha) and 1.5 times recommended dose (active ingredient 45 g/ha).The pymetrozine residues in soil and cotton leaf were less than 0.02 and 0.05 mg/kg at the 4th day in cotton dissipation experiment under field conditions . At harvest time, the residues of pymetrozine in cottonseed and soil were less than 0.05 and 0.02 mg/kg, respectively.