Abstract: A liquid chromatography-tandem mass spectroscopy (LC-MS/MS) method was developed for determining tetraconeazole residue in water and sediment system. The sediment samples were extracted with V(acetone):V(water)=9:1, and partitioned by dichloromethane liquid-liquid extraction, then cleaned up on neutral alumina and Florisil layer column. The water samples were prepared by dichloromethane liquid-liquid extraction and determined by LC-MS/MS. The results showed that when spiked from 0.5 to 5.0 μg/L, the average recoveries of tetraconazole in water were 89% to 98%, with relative standard deviations (RSDs) between 1.8% to 13%; when spiked from 0.5 to 5 μg/kg, the average recoveries in sediment were 97% to 103%, with RSDs between 6.3% to 11%; The limit of detection (LOD) was 2.0 pg, the limit of quantification(LOQ) in water and sediment were 0.5 μg/L and 0.5 μg/kg, respectively. The selectivity, reproducibility, accuracy and matrix effects were validated. The method was proved to be appropriate for determination of tetraconeazole residue in water and sediment system.