A method was developed for determination of free bisphenol A (BPA) in human milk by ultra-performance liquid chromatography and tandem mass spectrometry (UPLC-MS/MS). Methods BPA was ultrasonic extracted with methanol/acetone (1∶1, V/V), purified by freezing-lipid coupled with solid phase extraction (Waters Sep-Pak NH₂ 6cc), and then eluted with methanol/acetone (1∶1, V/V). Finally, BPA was separated on a Waters ACQUITYTM BEH C18column (50mm × 2.1mm×1.7μm) and detected by negative electrospray ionization in multiple reactions monitoring mode. ResultsThe linear range of BPA was 0.1-20μg/L, and the correlation coefficient (r²) of the standard curve was above 0.997. The mean recoveries for BPA with three spike levels were 91.85%-106.75%, and the relative standard deviations were 4.80%-15.36%. The limit of detection of the method was 0.010μg/L, and the limit of quantification was 0.035μg/L. Conclusion The method was proved to be suitable to evaluate the level of free BPA in human milk.