Objective: To compare the red-white aesthetic effects and masticatory function differences between light-cured nano resin and light-cured composite resin in the restoration of anterior tooth diastemas, providing a basis for clinical material selection. Methods: A prospective randomized controlled study was conducted, including 86 patients with anterior tooth diastemas ≤3mm, who were randomly divided into a nano resin group (44 cases, FiltekTM Supreme Ultra) and a composite resin group (42 cases, Herculite Ultra). Three months postoperatively, the red-white aesthetic effects (restoration morphology, color matching, marginal adaptation, gingival health) were evaluated using the modified USPHS criteria, and functional recovery was assessed using the T-ScanIII occlusal force analyzer and standardized masticatory efficiency tests. Results: The results showed that the nano resin group significantly outperformed the control group in red-white aesthetic scores, with notable differences in morphology matching (1.52±0.19 vs. 1.20±0.24), color matching (1.75±0.26 vs. 1.14±0.25), and gingival health scores (1.68±0.33 vs. 1.29±0.28) (P＜0.05). Conclusion: Light-cured nano resin achieves superior red-white aesthetic effects and masticatory function recovery in the restoration of anterior tooth gaps through the optical compatibility and interfacial mechanics optimization of nanoscale fillers. Its advantages stem from the bionic nature of filler particle size, low polymerization shrinkage, and the biomechanical compatibility of the elastic modulus with dental tissues.