Designing an active and selective catalyst for nonoxidative conversion of methane under mild conditions is critical for natural gas utilization as a chemical feedstock. Here, we demonstrate that the origin of the selective nonoxidative conversion of methane by the titanium carbide supported nickel cluster arises from the formation of a nickel carbide site under the reaction conditions, which could stabilize the CHx intermediate to facilitate the C-C coupling, but further coking is rather limited. The reaction mechanism reveals that the C2 products can be formed via a key -CHx-CH3 intermediate. In addition, we demonstrate that boration of the nickel cluster site can improve the methane conversion toward C2 products. That higher activity and selectivity from the moderate rise in d orbital energy levels can therefore be considered as a descriptor of the catalyst effectiveness. These findings provide an understanding of the dynamic behavior of the single nickel cluster toward methane conversion to C2 products and guidance for their future rational design.