We have studied the fragmentation behavior of positive and negative ions of taxoi and 6/8/6 type taxoids, the influence of different substituents on fragmentation, and the correlativity between fragmentation patterns and structure by MS/MS technique with different ionization methods such as FAB-MS, ESI-MS, ete. We have also investigated in detail the fragmentation of various molecular-related ions, such as [M+H]+, [M+Na]+ and [M-H] ions, and the formation pathways of characteristic fragment ions. It has been found that there exists some competing reaction between the loss of C-13 side chain and decomposition by loss of acetic acid. In addition, by comparing CID spectra obtained with low- and high-energy collision, it is seen that CID-MS/MS with low-energy collision is more suitable for the study of the structural analysis of small molecules and drug metabolites. The experimental results demonstrate that MS/MS spectra can reflect more effectively the slight difference of structure between the related com We have studied the fragmentation behavior of positive and negative ions of taxoi and 6/8/6 type taxoids, the influence of different substituents on fragmentation, and the correlativity between fragmentation patterns and structure by MS / MS technique with different ionization methods such as FAB -MS, ESI-MS, ete. We have also been involved in the fragmentation of various molecular-related ions, such as [M + H] +, [M + Na] + and [MH] ions, and the formation pathways of characteristic fragment ions. It has been found that there exists some competing reaction between the loss of C-13 side chain and decomposition by loss of acetic acid. In addition, by comparing CID spectra obtained with low- and high-energy collision, it is seen that CID-MS / MS with low-energy collision is more suitable for the study of the structural analysis of small molecules and drug metabolites. The experimental results demonstrate that MS / MS spectra can reflect more effectively the slight difference of structure betwe en the related com