An LC/MS method has been developed for the simultaneous quantification of five flavonoids, i.e., mosloflavone, negletein, gardenin B, 5-methoxy-6,7-methylenedioxyflavone, and 5,6,7-trimethoxyflavone, in different ultrasound assisted solvent extracts of Actinocarya tibetica. The chromatographic separation was achieved on a Chromolith Speed ROD RP-18e column with gradient elution using methanol and 0.1% formic acid in water. The calibration curves of all five analytes showed good linearity (R2>0.991). Accuracy and precision were within the required limits. The developed method could serve as an effective method for QC of A. tibetica. The investigated compounds were determined simultaneously for the first time in A. tibetica or any other plant.