An improved QuEChERs pretreatment method of 13 pesticide residues in aquatic products by liquid chromatography/tandem mass spectrometry （LC-MS/MS） was developed. The sample was extracted by 1%acidic acetonitrile and purified by polystyrene-divinylbenzene（PS-DVB） and primary secondary amine（PSA）. The analyte was ionized in the positive-ion electrospray ionization （ESI+） under multiple reaction monitoring （MRM） mode. Under optimized conditions， good linear relationship （R>0.99） was obtained in a concentration ranged from 1 to 100 μg/L by external standard method， and the limits of detection were range from 0.15 to 0.75 μg/kg. The recoveries of spiked aquatic product samples were found to be 75%-120% with RSDs under 15%（n=5）. The method was successfully applied in 12 fish and 18 shrimp， and the azoxystrobin was found in shrimps， the contents were 58.4 μg/kg and 38.6 μg/kg. The results indicated that the rapid cost-effective accurate method was proved successful in the determination of pesticide residues in aquatic samples. Furthermore， the method is more commercial than other QuEChERS methods with advantage of low cost of PS-DVB.