Abstract: 篈 new type of mass spectrometrical characteristic fragmentation pattern has beenfound based on our observation and researches for years and used for fragmentation interpretation of a bigger kind of organic compounds in which there must be 1, 2 and 5, 6-double bonds and a transferable 7-hydrogen atom as the structural characteristics. Thefragmentation pattern has been inferred as follows:and the fragmentation pattern can be called eight membered ring transition state hydrogen rearrangement β-cleavage. This should be the sixth characteristic fragmentationpattern in organic mass spectromctry on chcmistry structurcs (the other five are α-cleavage, benzyl cleavage, allylic cleavage, Mclafferty rearrangement cleavage and RDA cleavage) and the worthiness for practical purpose and the fragmentation intensity would behigher than those of the allylic cleavage and close to McLafferty rearrangement cleavageand RDA cleavage. The new fragmentation pattern has been proved by Thomas and his colleagues,deuterium label experiments