Abstract: Based on ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS), the adduct ions formed by three tobacco polyphenols, including chlorogenic acid, scopoletin and rutoside, were studied in either positive/negative electrospray ionization mode. The effects of mobile phase composition on the form, abundance and intensity of polyphenol adduct ions were investigated. The results showed that: 1) In negative ion mode, the major ion form of all the three polyphenols was M-H^- with an abundance of more than 96%, and thus the formation of the other adduct ions had a limited effect on quantification. However, the mobile phase composition had certain effects on the form of the chlorogenic acid and rutoside adduct ions and the intensities of the adduct ions of the three polyphenols tested. 2) In the positive ion mode, the mobile phase composition had no significant effect on the forms of the polyphenol adduct ions. However, it had significant effects on the abundances and intensities of the polyphenol adduct ions, which were also related to the structures of the polyphenols. 3) Differences in the fragmentation patterns of different adduct ions were generated and used in identifying the compound structure and could improve the accuracy of qualitative analysis.