Objective To investigate the clinical efficacy of cold light whitening technology and night guard vital bleaching technology in the treatment of tetracycline tooth. Methods A total of 96 patients with tetracycline tooth admitted to Harbin Stomatological Hospital from January to December 2022 were selected as the research objects. They were divided into control group and experimental group by random number table method, with 48 patients in each group. The control group was treated with cold light whitening technology, and the experimental group was treated with cold light whitening technology combined with night guard vital bleaching technology. The therapeutic effect, whitening effect and tooth sensitivity of the two groups were compared. Results The total effective rate of treatment in the experimental group was 95.83%, which was higher than 75.00% in the experimental group (P <0.05). The proportion of normal color in experimental group was higher than that in control group (P <0.05). After treatment, the tooth sensitivity of the experimental group was 12.50%, which was lower than 27.08% of the control group, but the difference was not statistically significant (P >0.05). Conclusion The combination of cold light whitening technology and night guard vital bleaching technology is effective in the treatment of tetracycline tooth, which can improve the level and the color of tooth. After treatment, the sensitivity of patients' tooth is low, which is worthy of clinical application.