Abstract: Fumonisin B1 in maize was determined by liquid chromatography/tandem mass spectrometry. The analysis was extracted from maize samples by acetonitrile-water-acetic acid 49:50:1(V/V/V). Raw extracts were evaporated to dryness and dissolved with mobile phase, chromatographyed on a C₁₈ column, and detection was performed on a triple quadrupole tandem mass spectrometry with electrospray ionization source. The method has a limit of quantification of 10 µg•kg^－1 in maize samples. The calibration curve is linear in the range of 1-500 µg•L^－1. The mean recovery ranges from 94 % to 104 %, and the relative standard derivations are lower than 9%. The method is sensitive and specific to be applied for determination of fumonisin B1 in maize samples.