Abstract: A method was established for the determination of quinclorac in paddy soil, paddy water and rice plants by liquid chromatography tandem triple quadrupole mass spectrometry. The sample was extracted with V(formic acid):V(acetonitrile)=2:98. Then the samples were purified by two dispersed solid phase extraction adsorbents of C₁₈ and PSA. With 0.01% (V/V) formic acid-aqueous as the mobile phase gradient elution, the target compound was separated using reversed-phase liquid chromatography column. The samples were detected with positive electrospray ionization (ESI⁺) in multiple reaction monitoring mode, and quantified by external standard method. The result showed that the linear relationship of quinclorac in the linear range from 0.01 to 1 mg/L was good (r ≥ 0.999). The limit of quantification of quinclorac was 0.0125-0.05 mg/kg. When the spiked levels of quinclorac in soil and plants were 0.05, 0.2 and 1 mg/kg, and the spiked levels in field water were 0.0125, 0.05 and 0.25 mg/kg, the average recovery rates ranged from 85% to 112%. The relative standard deviations (RSD, n = 6) varied from 1.1% to 9.3%. The reliability of the method was verified using a pot experiment. Quinclorac was sprayed onto the rice seedlings at a dose of 375 g/hm². The results showed that quinclorac was rapidly degraded in rice plants. 21 days after application, the dissipation rate of quinclorac was 94%. But the dissipation rates of quinclorac in paddy water and soil were slow. 21 days after the treatment, the dissipation rates were only 33% and 45%, respectively. This analytical method is easy to operate, sensitive, fast and stable. It is suitable to detect the quinclorac in paddy soil, paddy water and rice plants.