Spatholobi Caulis, the vine stem of Spatholobus suberectus Dunn, has been widely used in traditional Chinese and folk medicines for treatment of irregular menstruation, blood deficiency and rheumatalgia in clinic. In this study, an accurate and reliable high performance liquid chromatography/electrospray ionization triple quadrupole mass spectrometry (HPLC–MS/MS) method was established for simultaneous determination of 16 phenolic bioactive constituents, including five flavanols, seven isoflavonoids, three flavanones and one chalcone in Spatholobi Caulis. The method validation results exhibited that the developed method had desirable specificity, linearity, precision and accuracy. The quantitative analysis results showed that flavanols were the abundant constituents in Spatholobi Caulis. Moreover, principal component analysis (PCA) was performed to assess the quality variation of samples collected from different regions in China. The PCA results indicated the quantitative analysis based on HPLC–MS/MS is a feasible method for quality assessment and control of Spatholobi Caulis.