This work reports a very facile method to fabricate ultra-small PdO nanoclusters supported on carbon nanofibers (CNFs) which performed outstanding catalytic activity for Suzuki coupling reaction under the mild reaction conditions. The catalyst developed in this paper showed several advantages compared with our group previous jobs, such as simpler procedure to prepare the catalyst, lower active species loading and higher performance in Suzuki coupling reactions. Importantly, the catalyst could be recycled at least up to ten times and without any loss in activity. The reaction mechanism in this system was also explored by our group.Graphical AbstractUltra-small palladium oxide nanoclusters supported on carbon nanofibers (PdO@CNFs) were successfully obtained through the facile process of electrospinning technology and high-temperature carbonization. The fabricated composite catalyst exhibited a better catalytic activity for Suzuki coupling reaction under mild conditions, especially in recycle ability (at least ten times). According to the experiment results, a plausible reaction mechanism was proposed by our group. We had an idea that the active species was palladium oxide, and the first step involved the reaction between bromobenzene and palladium oxide nanoclusters generated organo-oxopalladium species. This step was a rate-determining step and slightly different from the traditional mechanism. [GRAPHICS] .