Modulating the surface coordination environment of Pt based nanocrystals at the atomic level is of great importance to obtain good electrocatalytic performance. Given the fundamental understandings of surface structure degeneration of Pt based nanocrystals, introducing a weak electronegative element to the surface of Pt-based catalysts is beneficial for suppressing surface passivation and improving hydrogen evolution reaction performance of Pt. Density functional theory results reveal that the energy barrier of water dissociation process can be greatly reduced by using Se element as the surface modifier to replace the O. This hypothesis is further validated by experiments that ultralong Pt₈₅Mo₁₅-Se nanowires were fabricated to suppress the excessive passivation behavior of transition metals of Pt based alloy. The Pt₈₅Mo₁₅-Se nanowires exhibit higher activity with 4.98 times the specific activity and 4.87 times the mass activity of commercial Pt/C, as well as a better stability towards alkaline hydrogen evolution reaction. The deep exploration of X-ray photoelectron spectroscopy and theoretical calculations disclose that Se element could maintain the electron-rich state around the electronic orbit of Pt. This study provides a new insight to advance the fundamental understanding on electrocatalytic materials, which exhibits a promising approach to protect the surface chemical environment of Pt based nanocrystals.