Abstract: Copper nitride (Cu₃N) films were fabricated by magnetron sputtering under different gas flow ratios, and the correlation mechanism between the structure and the electrocatalytic hydrogen evolution performance was investigated. The results showed that as the gas flow ratio (R) increased from 0.05 to 0.25, the nitrogen content in the film significantly increased from 16.08% to 30.15%, while the copper content decreased accordingly. When R is 0.20, the optical bandgap of Cu₃N thin film is the smallest (1.32 eV), and its electrocatalytic hydrogen evolution performance is optimal, with overpotential and Tafel slope of 317.76 mV and 259.28 mV·dec⁻¹, respectively. The results showed that copper enrichment changed the electronic structure and active site distribution of Cu₃N thin films, enhancing the activity of the hydrogen evolution reaction. This study provides technical reference for the preparation of Cu₃N thin films and their application in the field of hydrogen energy controlled by gas flow ratio.