The multiple chemical constituents contained in Erxian Decoction (EXD) were simultaneously analyzed by the established LC-DAD-MS/MS method for the first time. The HPLC separation was carried out on an XBridgeTM C18 column ( 4.6 mm x 250 mm , 5.0 µm) with a linear gradient elution of solvent A (ultra-pure water contains 0.1% formic acid , 2 mM ammonium acetate ) and B (acetonitrile). The UV detection was achieved at the wavelength of 280 and 345 nm . Through the online ESI - MSn analysis , a total of 54 chemical constituents have been identified or tentatively characterized in positive or negative ESI-MS mode, and 23 of them were unambiguously identified by comparing the retention time, UV spectra and MS fragmentation patterns with the authentic ones. The established LC-DAD-MS method was proved to be simple, accurate and applicable for the simultaneously identification of the chemical constituents contained in EXD. The results indicated that the EXD contains several groups of natural products, which possibly contribute to its integrative clinical effect for menopausal syndromes.