Objective: To explore the effect of cold light whitening system on discolored teeth. Methods: From June 2023 to October 2024, 80 patients with discolored teeth were randomly divided into two groups, 40 cases in each group. The control group was whitened with 15% hydrogen peroxide whitening denture base, and the observation group was whitened with cold light whitening system. The overall tooth discoloration (ΔE*), dentine hypersensitivity, gingivitis, patient satisfaction and the occurrence of external absorption of teeth and neck were compared between the two groups at 2 weeks, 3 months, 6 months and 1 year after treatment. Results: The ΔE* values of the observation group were higher than those of the control group at 2 weeks, 3 months, 6 months and 12 months after whitening, and the difference was statistically significant (P < 0.05). There was no significant difference in the incidence of dentine hypersensitivity and gingivitis between the two groups (P > 0.05). The satisfaction of the observation group was higher than that of the control group (P < 0.05). There was no significant difference in the incidence of external absorption between the two groups (P > 0.05). Conclusion: Cold light whitening system is a safe and effective way to treat discolored teeth, which can better meet the tooth whitening needs of patients with discolored teeth.