Residue dynamics of acetamiprid in watermelon and soil was studied in this paper utilizing liquid chromatography with tandem mass spectrometry (LC-MS/MS). The LODs for acetamiprid in whole watermelon, melon flesh and soil were 0.002 mg/kg. The fortified recoveries ranged from 73.7% to 107.5% with relative standard deviations (RSDs) of 1.7%-5.9%. Acetamiprid dissipated in watermelon and soil with the half-life 3.12-3.92 days and 1.18-1.46 days in two locations Beijing and Shandong provinces, respectively. In the terminal residue experiment, no higher residue than 0.01 mg/kg in melon flesh and 0.3 mg/kg in whole watermelon and soil were detected.