Hydrogen economy, as the most promising alternative energy system, relies on the hydrogen production through sustainable water splitting which in turn relies on the high efficiency electrocatalysts. PtAuCu A1-phase alloy has been predicted to be a promising electrocatalyst for the hydrogen evolution. As such preferred phase of Pt-Au-Cu is not thermodynamically favored, herein, we stabilize PtAuCu alloy by engineering the high-entropy phase in the form of nanowire. Density functional theory (DFT) calculations indicate that, in comparison with the ordered phase and segregated phases with discrete hydrogen binding energy, the high-entropy phase provides a diverse combination of site composition to continuously tune the hydrogen binding energy, and thus generate a series of highly active sites for the hydrogen evolution. Reflecting the theoretical prediction, electrochemical tests show that the A1-phase PtAuCu nanowire significantly outperforms its nanoparticle counterpart with phase segregation, toward the electrocatalysis of hydrogen evolution, offering one of the best hydrogen evolution electrocatalysts.