Abstract: The activation of H₂ on MnO₂ is studied by density functional theory calculation, in which it is found that the distance of "Mn-O" plays a key role for the activation of H₂, that is, the longer the Mn-O distance, the more activation of H₂, and the most activation occurs at the 0.4 nm(i.e., a "Frustrated Lewis acid-base pair" is formed). Through the analysis of the electronic structure properties and interaction of theH…H^≠transition state (TSs), it is found the "Mn-O active pair" that can form a "Frustrated Lewis acid-base pair" has the largest overall interaction energy and thus stabilizes the TSs. The present results may help people to understand the nature of the synergistic effect of the "Frustrated Lewis acid-base pair", and construct a highly active "Frustrated Lewis acid-base pair" by adjusting the microstructure of the catalyst more efficiently.