In this paper,the positional isomers of monocaffeoylquinic acid and dicaffeoylquinic acid were separated and analyzed by liquid chromatography(LC),then analyzed by tandem mass spectrometry(MS/MS) with different collision energies.The fragmentation rules for the analytes were investigated using MS/MS.For the positional isomers of monocaffeoylquinic acid,as the intensities of their parent ion 377 and product ion 163 changed significantly under different collision energies,they could be distinguished by the intensity ratios of 377/163.The isomers with intensity ratios of 377/163 in turn were 3-O-caffeoylquinic acid,4-O-caffeoylquinic acid and 5-O-caffeoylquinic acid.As for the positional isomers of dicaffeoylquinic acid,the intensities of their parent ion 539 and product ions 377 and 163 changed significantly under different collision energies,they could be distinguished by their intensity ratios of 539/377 and 377/163.The isomers with intensity ratios of 539/377 in turn were 4,5-di-O-caffeoylquinic acid,3,4-di-O-caffeoylquinic acid and 3,5-di-O-caffeoylquinic acid,while the isomers with intensity ratios of 377/163 in order were 3,5-di-O-caffeoylquinic acid,4,5-di-O-caffeoylquinic acid and 3,4-di-O-caffeoylquinic acid.The positional isomers of caffeoquinic acid were separated and analyzed based on an Agilent Poroshell 120 SB-Aq C18 column,and the eluting orders were as follows:5-O-caffeoylquinic acid,4-O-caffeoylquinic acid,3-O-caffeoylquinic acid,3,4-di-O-caffeoylquinic acid,3,5-di-O-caffeoylquinic acid and 4,5-di-O-caffeoylquinic acid.The positional isomers of caffeoylquinic acid in honeysuckle were identified accurately based on the chromatographic retention and MS/MS characteristics.