Deep insight of reaction mechanism in lignin model compounds is helpful to achieve the directed depolymerization of lignin or biomass to chemicals or fuels. In this study, the density functional theory (DFT) calculation was employed to investigate the cleavage mechanism of the C-O bonds in lignin di-mers. Additionally, the intrinsic chemical reactivity of molecular in term of the Fukui function was applied to predict the most probable sites which react with hydrogen free radicals (H center dot). It was found that the O atoms in lignin dimers are the most reaction site involving H center dot because of the large f (0). By this method, the most rational path from a series of reaction paths was screen out. Apart from the Fukui function, the average local ionization energy (ALIE) was analyzed to prove the reliability of Fukui function. The kinetic analysis of the reaction path was performed to further understand the impact of temperature on the reaction rate constant (KTST). It is observed that benzyl phenyl ether (BPE) with higher KTST could be easily cleaved because of the relatively low energy barrier. (C) 2020 Elsevier Ltd. All rights reserved.