Objective：To evaluate the thickness of buccal cortical bone at different height in posterior area of maxilla and mandible where mini-plants was inserted． Methods：Thirty cone-beam CT（CBCT） images were selected from the Affilited Stomatology Hospi－tal，Chongqing Medical University. Thickness of cortical bone between canine distal and second molar mesial at the height of 3，5，and 7 mm from the alveolar crest was determined. The data were analyzed statistically. Results：The thickness of buccal cortical bone in the mandible posterior area was greater than that of maxilla（P＜0.001）. Between canine and first molar in maxilla the thickness was the minimum at the height of 5 mm from the alveolar crest.The thickness of cortical bone between first molar and second molar in maxilla and mandible became greater along with the distance increase from the alveolar crest. Conclusion：The thickness of buccal cortical bone changes along with the position changing sagittally and vertically，which should be considered in mini-plants implanta－tion. Between canine and first molar in maxilla，a position as far from or close to the alveolar crest as possible is optimal，while in mandible and between first molar and second molar in maxilla，a position as far from the alveolar crest as possible is the best.