A simple method was developed for simultaneous determination of seven urinary metabolites of organophosphate esters by liquid chromatography-tandem mass spectrometry (LC-MS / MS). Based on different physical and chemical properties of these OPs metabolites, the solid phase extraction cartridges and the washing and eluting solvents were optimized in details. Furthermore, the mobile phase and mass spectrometric parameters were also investigated. The results showed that Oasis WAX cartridge was the best SPE column in this study, and 2 mL of NH3 ·H2 O (5% ) in methanol and 2 mL of methanol were chosen as the eluting solvents. The recoveries of six analytes were ranged from 60. 5% to 104. 0% , whereas DEP ranged from 17. 8% to 36. 2% . Seven analytes could be baseline separated from each other under the optimized chromatographic conditions. The limits of detection and quantification of seven analytes ranged from 0. 005 to 0. 2 μg / L and 0. 02 to 0. 5 μg / L, respectively. The standard deviations of response repeatability for intra-day and inter-day period were lower than 15. 4% . This method was finally applied to determination of metabolites of OPs from 10 urines from general population in Guangzhou city. The concentrations of total OPs metabolites in urine samples ranged from 0. 5 to 6. 7 μg / L.