Abstract: Abstract：　Objective　Using CBCT to evaluate the amount of labial and palatal alveolar in the root apex area of the maxillary central incisor in the skeletal class II adults before orthodontic treatment, and analyzing the related factors about the labial and palatal alveolar of the maxillary central incisors. Methods　The apical horizontal reference plane was the LA plane. The plane 3mm above the LA plane was the LU plane and the plane 3mm below the LA plane was the LL plane. In the LA plane, the distances from the apex to the labial and palatal alveolar are L1 and L2 respectively and LT1 was L1 and L2. In the LU plane, the distances from the intersection of the long axial of the incisor and the LU plane to the labial and palatal alveolar are L3 and L4 respectively and LT2 was L3 and L4. In the LL plane, the distance from the intersection point of the LL plane and the labial side to the labial alveolar was L5, the distance from the intersection point of the LL plane and the palatal side to the palatal alveolar was L6, and the distance from the intersection point of the LL plane to the labial and palatal alveolar was LT3.θ1 was the Angle between the palatal plane and the axis of the incisor, andθ2 was the angle between the palatal plane and the perpendicular line of the midpoint of the lip and palate alveolar crest. Results　θ1 was positively correlated with L1、L3 and L5.θ2 was positively correlated with L2、LT1、L4、LT2、L6、LT3 and negatively correlated with L1、L3、L5. SN-MP is negatively correlated with L1、LT1、L3 and LT2. SNA is positively correlated with L2、L4、L6 and LT3. Conclusions　The results showed that the thickness of maxillary central incisors labial and palatal alveolar in skeletal class II adults was closely correlated with the inclination of maxillary central incisors，the inclination of alveolar crest and the vertical dimension, among which the inclination of maxillary central incisors and the vertical dimension had the greatest influence on the thickness of maxillary central incisors labial alveolar bone.

Key words: skeletal class II, maxillary central incisor, alveolar bone, CBCT