Abstract: Carbon nitride (g-C₃N₄) is one of the most promising nonmetallic photocatalysts, yet its unique electronic structure limits the separation efficiency of photogenerated carriers within the molecule, thereby affecting its photocatalytic activity. To address this limitation, thymine-doped graphitic carbon nitride(T-C₃N₄) was synthesized via thermal polycondensation of thiourea and thymine.Doping thymine significantly enhances the separation efficiency of photogenerated carriers and regulates the band gap, broadening the visible light absorption range of g-C₃N₄.The photocatalytic hydrogen production results show that under visible light irradiation (λ > 420 nm), T₂₀-C₃N₄ exhibits the best photocatalytic hydrogen production performance, reaching 405.86 µmol·g⁻¹·h⁻¹, which is 6.61 times higher than that of pristine g-C₃N₄ (61.37 µmol·g⁻¹·h⁻¹).After three cycles of experiments, the hydrogen production performance of the sample did not show a significant decrease, indicating that T₂₀-C₃N₄ has good stability.