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BACKGROUND: A review of previous epidemiological investigations shows that the detection rate of malocclusion is the highest in Angle I, but the classification is limited by the failure to consider the comprehensive mechanism of the formation of malocclusion in the three-dimensional direction of the length, width and height of teeth, jaws and facial structures, and the profound impact of the position of the mandible and facial bones on a person’s appearance. Therefore, the morphological characteristics of the mandible and chin should be fully considered before orthodontic treatment. OBJECTIVE: To compare the similarities and differences of the three-dimensional facial morphology in adult females with different vertical skeletal types of skeletal Class I by measuring the three-dimensional morphology of the chins and mandibles through cone-beam CT multi-planar reconstruction. METHODS: According to SN-MP angle, the cone-beam CT images of 86 females with skeletal Class I aged from 18 to 35 years were imported into MIMCS19.0 to make multi-planar reconstruction, and then the data was divided into three groups: < 29° (low angle group, 30 cases), 29°-39° (average angle group, 30 cases), and > 39° (high angle group, 26 cases). Then, the mandibular linear distance and angle were measured, and the mandibular outline was measured through the three-dimensional reconstruction. RESULTS AND CONCLUSION: With the increase of mandibular plane angle, the morphology of mandible tended to be: (1) the mandible ascending ramus became shorter, and the mandible body grew; (2) the notch of mandibular angle deepened gradually, and the opening of the mandibular angle increased gradually relative to the cranial-jaw; (3) the alveolar process of the chin became longer and the shape of chin became gentle; (4) counterclockwise rotation of the chin and compensatory inclination of lower anterior teeth towards tongue occurred. Comparing different vertical skeletal types of skeletal Class I in adult females, both the morphologies of the mandible and chin are different, and the mandibular plane angle is related to the morphology of the mandible and chin. [ABSTRACT FROM AUTHOR]