Abstract: Fragmentation pathways of periplocoside A and E were investigated by electrospray ionization multi-stage tandem mass spectrometry. One of the major fragments observed in the collision induced dissociation (CID) spectrum were produced by losing disubstituted pyranone from quasi-molecular of periplocoside A. The cleavage and rearrangement of the agalycone ring D,accompanied by the neutral lose of formaldehyde (-30Da),as well as the lose of various sugar chains,were the important structure characteristic,and could be used to identify the molecular skeleton. Identification of periplocosides was summerized by investigating the fragmentation pathway and characteristic ions of periplocoside A and E,and the structure of periplocoside X,an unreported compound isolated from the root bark of Periploca sepium,was proposed. These results might be used to investigate the distribution and structures of periplocosides in Periploca sepium.