Abstract: The major chemical constituents of Ephedra（ephedrine, pseudoephedrine, methylephedrine, norephedrine）were analyzed by electrospray ionization tandem-mass spectrometry. Major chemical components, including Ephedrine, Pseudoephedrine, Methylephedrine, Norephedrine were studied. Using tandem mass spectrometry, useful fragments of Ephedrine, Pseudoephedrine, Methylephedrine, Norephedrine were obtained. The experimental results demonstrate that Ephedrine and Pseudoephedrine show the similar fragmentation in ESI-MS.