Abstract: A method was developed for determination of highly polar fungicide fosetyl-aluminium in plant-derived product of tomato, cabbage, grape, flammulina velutipes, rice, peanut by using liquid chromatography-tandem mass spectrometry. The best experimental conditions were established by optimization of chromatogram, mass spectrum and pretreatment. Sample was extracted with acetonitrile and purified by HLB solid phase extraction cartridges. Separation was performed on the AQ C₁₈ column. The mobile phase consisted of methanol and 0.15% formic acid solution. The sample was analyzed by gradient elution and the flow rate was 0.1~0.2 mL/min. The mass spectrometer was operated in the negative ion mode (ESI⁻) using select reaction monitoring (SRM). Isotopically labelled internal standard calibration curve was used for quantitative analysis. Results showed that there was a good linearity for fosetyl-aluminium in the range of 20.0～800.0 ng/mL with a determination coefficient (r²) of 0.9904. The limit of quantitation in the method was 100.0 μg/kg. The average recoveries of fosetyl-aluminium at three levels were in the range of 69.6%~112.3%, the RSDs were 1.0%~9.8%. The method is simple and sensitive, and can meet the requirements of domestic and foreign standards and regulations on the residual limit of fosetyl-aluminium in plant-derived products.