Coordination tunability of the single-atom catalysts (SACs) is an essential but challenging issue for the catalyst sifting and structure-activity relationship analysis. Herein, Pt single atoms with tunable coordination are readily achieved via a facile cold-plasma technique by changing the gas type (N2, Ar, or Air) and treatment duration. Combining with density functional theory calculation, the Pt-N coordination concentration is predicted to be highly correlated with adsorption free energy of H* atoms (ΔGH*) for the hydrogen evolution reaction (HER), which is further validated experimentally. Remarkably, the sample with N, O co-dopant introduced by air plasma exhibits a high TOF of ∼13 H2 s−1 at 40 mV, and outstanding mass activity of 7.41 A mg−1Pt for HER, which is 26.5 times of commercial Pt/C catalyst. The enhanced performance might originate from the optimized electronic structure of active carbon site with moderate electron transfer and p-band center, which enables a suitable binding strength with H* and thus a near-zero ΔGH*.