To elucidate the mechanism of LiP catalysis and pH effects on the ET rate, we performed multi-scale simulations on the one-electron oxidation of lignin mediated by Cpd I (stage II in Scheme 1), with and without the acid buffer of tartaric acid, respectively. Moreover, we also calculated the ET and PCET rates involved in this process by using the nonadiabatic ET and PCET theories. Our study provided a molecular basis of how pH regulates the reaction mechanism and kinetics of long-range ET, highlighting that forming/disforming hydrogen bonds can be used as a practical strategy to regulate the long-range ET reactions.