To investigate the fragmentation rule of Herba Epimedii flavonoids by high resolution mass spectrometry (HR-MS),and to identify the chemical structures of the new compounds.Q-TOF was used to collect data,and PeakView software was used to analyze the known components qualitatively.With the help of Mass Calculators,Formula Finder,Fragments Pane and other functions of the software,the fragmentation rules of compounds were analyzed and summarized.A total of 27 compounds were identified from 15 varieties of Herba Epimedii in 54 batches.In the mass spectrometry containing ESI,the characteristic flavonoids will break the glycosidic bond at C-3 position and C-7 position successively from the outside to the inside,and then the isoamyl group at the C-8 position and the methoxy group at the C-4′ position are removed.If the acetyl group is bonded on the glycoside,the acetyl group will be removed first in the mass spectrometry.If the double bond of Isoamyl group at the C-8 position is reduced to isoamyl alcohol group,the group will be dehydrated first and then removed If the C-8 and C-7 groups form a ring,the characteristic fragments of isopentenyl will not be produced.The chemical structures of two new compounds are also identified.This method is simple,practical and reliable.The experimental results will help to further clarify the pharmacodynamic material basis and biosynthesis law of Herba Epimedii.