Designing electrocatalysts with superior activity and stability to Pt/C for the highly efficient pH-universal electrochemical hydrogen evolution reaction (HER) still remains an urgent challenge. Herein, we report a facile plasma method for the preparation of defect-rich flexible carbon cloth decorated with ultralow-loading (0.1 wt%) PtRu alloyed nanoclusters (PtRu/CC-P) to resolve these problems. Remarkably, the developed PtRu/CC-P catalyst delivered a high mass activity of 3.77 A mg -1 ( η = 100 mV), almost 3.6 times higher than that of the benchmark HER electrocatalyst 20%Pt/C (1.05 A mg -1 ). Meanwhile, it only required a low overpotential of 44 mV to achieve a current density of 10 mA cm -2 in alkaline media. Systematic experimental and DFT calculation results revealed that the Pt-Ru bridge of PtRu alloyed nanoclusters in PtRu/CC-P can optimize the adsorption strength of HER intermediates at active sites, decrease the H 2 O dissociation energy barrier, and consequently facilitate the HER kinetics. Inspiringly, when the PtRu content was increased to 1 wt%, PtRu/CC-P still exhibited a relatively low overpotential of 276 mV even at a high current density of 1000 mA cm -2 and maintained excellent durability at a relatively high current density of 50-500 mA cm -2 for more than 15 h in alkaline media. In addition, PtRu/CC-P also showed brilliant HER activity and stability in neutral and acidic media. This facile method provides a feasible route for the rational design of Pt-based alloyed catalysts toward industrial hydrogen production at all-pH values.