To study the application effect of laser technology in tooth whitening. Methods A total of 100 patients who underwent tooth whitening admitted to our hospital from January 2018 to January 2022 were selected as the research objects. According to the random number table method, they were divided into group A and group B, with 50 patients in each group. Group A was treated with cold light, and group B was treated with semiconductor laser. The therapeutic effect, incidence of adverse reactions and treatment time were compared between the two groups. Results The total effective rate in group B was 96.00%, which was higher than 84.00% in group A (P <0.05). After 6 months of follow-up, the incidence of adverse reactions in group B was 4.00%, which was lower than 18.00% in group A (P <0.05). The treatment time of group B was (72.19±3.28) min, which was shorter than (86.39±4.82) min of group A (P <0.05). Conclusion The effect of laser technology for tooth whitening is good, the treatment time is short, and the incidence of adverse reactions of tooth discoloration and gingival sensitivity is low in the late follow-up period, which is worthy of clinical application.