Objective To analyze the application value of CBCT in preoperative risk assessment of impacted mandibular third molar. Methods From June 2020 to May 2022, 50 patients (72 sides of impacted mandibular third molar) who underwent extraction of impacted mandibular third molar in oral and maxillofacial surgery of our hospital were selected as the research objects. All patients underwent CBCT examination. The risk of inferior alveolar nerve injury during impacted mandibular third molar extraction was evaluated by our hospital physician according to panoramic radiographs and CBCT images, and the surgical path was designed to compare the differences between the two imaging data. Results There was no significant difference in the proportion of root over the inferior wall of mandibular canal between the two imaging results (P >0.05). The proportion of close contact between the root and the upper wall of the mandibular canal in CBCT images was higher than that in panoramic radiographs, and the proportion of lateral root inserted into the mandibular canal was lower than that in panoramic radiographs (P <0.05). The extraction of impacted mandibular third molar may lead to the risk of inferior alveolar nerve injury. The risk of nerve injury in CBCT images was lower than that in panoramic radiographs (P <0.05). According to the preoperative CBCT image, the proportion of patients with clear removal of bone resistance, separation of teeth, insertion of teeth, and direction of tooth dislocation was higher than that of curved tomography (P <0.05). Conclusion The information provided by CBCT images can provide more accurate guidance for selecting a reasonable surgical path. Clinicians can accurately evaluate the three-dimensional image space distance between impacted molars and mandibular canal according to the results of CBCT images, so as to better assist surgical treatment.