Orthodontic patients often suffer from mucosal discomfort due to the friction stimulation of orthodontic components on the oral mucosa, and semiconductor laser can treat the oral mucosal discomfort caused by orthodontic treatment, such as redness, swelling, ulcers, etc. This study innovatively created a persistent traumatic environment in the mouth of rats to simulate the intraoral conditions of orthodontic patients, with the aim of using animal models to broaden the understanding of semiconductor laser repair mechanisms of orthodontic traumatic ulcers. 32 male Wistar rats were randomly divided into 6 groups: 1) blank control group;2) control group; 3) chlorhexidine group; 4) laser group 1; 5) laser group 2; 6) laser group 3. The research contents included ulcer healing degree score, enzyme-linked immunosorbent assay, histological observation of stained sections of ulcer tissue, and analysis of microbial attachment on ulcer surface. The results showed that the continuous traumatic environment significantly prolonged the healing time of ulcer (P<0.05). During the ulcer duration, the proinflammatory factor level was lower, the anti-inflammatory factor level was higher and the healing score was better in the laser group (P<0.05). The antibacterial effect of semiconductor laser is less than 0.12% chlorhexidine solution; Hematoxylin-eosin tissue sections showed lower inflammatory cell infiltration and better epi-thelial healing in the laser group. This study shows that continuous traumatic environment can delay ulcer healing, and semiconductor laser with appropriate irradiation time is superior to traditional 0.12% chlorhexidine solution in reducing inflammation, relieving pain and promoting ulcer tissue healing. Compared with previous studies, the animal model in this study has made some progress and is closer to the real oral conditions of orthodontic patients. The results further demonstrated the potential of semiconductor laser in the treatment of oral traumatic ulcers during orthodontics.