The integration of carbon dots (CDs) with graphitic carbon nitride (g-C₃N₄) has emerged as a promising approach to enhance photocatalytic hydrogen (H₂) evolution. Despite significant progress, critical challenges remain in achieving broad visible-light absorption and suppressing charge recombination. In this work, we developed a series of photocatalysts through in situ embedding of red-emissive CDs (R-CDs) into g-C₃N₄ (RCN) with precisely controlled loading amounts. Systematic characterization revealed that the R-CDs incorporation simultaneously addresses two fundamental limitations: (1) extending the light absorption edge to 800 nm, and (2) acting as an electron acceptor, facilitating charge separation. The optimized RCN composite demonstrates exceptional H₂ evolution activity (1.87 mmol·g⁻¹·h⁻¹, wavelength (λ) ≥ 420 nm), representing a 3.3-fold enhancement over pristine g-C₃N₄. Remarkably, the apparent quantum efficiency (AQE) reaches 9.1% at 420 nm, while maintaining measurable activity beyond 475 nm, where unmodified g-C₃N₄ shows negligible response. This study provides fundamental insights into band structure engineering and charge carrier management through rational design of CDs-modified semiconductor heterostructures.