Background/purpose: The present study was performed to compare the ethnic features of alveolar bone of Li and Han nationality in Hainan province. Methods: The lower first permanent mandibular molar tooth (L6) from patients with Li nationality and Han nationality were chosen. Cone-beam computed tomography (CBCT) examination technology was used to measure the vertical height of the middle point of the crown of L6 along the long axis of the tooth from the crest of alveolar bone to the inferior alveolar nerve canal (IANC), and the buccolingual width of alveolar ridge in the direction of this site. The vertical height and buccolingual width between Li nationality and Han nationality were compared. Results: The vertical height between the crest of alveolar bone to IANC of L6 in Li nationality was farther than that in Han nationality and the difference was statistically significant. There was no significant difference in the buccolingual width of alveolar ridge. At the same time, the comparison of the same gender group shows that the difference between the two indicators remains unchanged. Conclusion: Ethnicity-related variations exist in terms of the length of alveolar crest to IANC in the mandible. Longer implants could be considered in the restoration of L6 loss in Li nationality.