Abstract: Objective To develop a quantitative method for determination of pyrethroid insecticide metabolites (3-PBA, Cis-Cl₂C and Trans-Cl₂CA) in human urine by liquid chromatography-tandem quadrupole mass spectrometry.Methods After acidification and liquid-liquid extraction, the urine samples were analyzed by C₁₈ separation, MS detector and internal standard quantification.Results A good liner relationship was obtained and the correlation coefficient were greater than 0.998. Interday/Intraday relative standard deviation. (RSD) and recoveries determined by analysing fortified manual synthesis urine were less than 10.0% and 90.0-110.0% respectively. Limits of detection were 0.20 μg/L.Conclusion As it is easy,convenient and low cost,the method can meet biomonitoring requirements for general or special populations.