Objective To quantitatively evaluate the thickness of the buccal cortical bone in the posterior region of the maxillary for orthodontic micro‐implants in children .Methods Forty children (20 males and 20 females) in permanent dentition with Class Ⅱdivision 1 malocclusion were selected .The maxillary posterior alveolar bones of the subjects were scanned and reconstructed by cone‐beam computed tomography (CBCT) .The thickness of the cortical bone between the dental roots of the second upper premolar and the first upper molar at the height of 3 ,4 ,5 ,6 ,7 ,8 ,9 mm from the alveolar crest were determined .The data were analyzed sta‐tistically .Results The thickness of the cortical bone between the second upper premolar and the first upper molar was minimum at the height of 4 mm from the alveolar crest(P<0 .05) .The thickness of the cortical bone increased along with the distance increas‐ing from the alveolar crest at the height of 5 mm .The cortical bones in male were significantly thicker than those in female at the height of 7 ,8 ,9 mm (P<0 .05) .Conclusion The thickness of the buccal corticalbone in children in permanent dentition with ClassⅡ division 1 malocclusion changes with the measured vertical position .Micro‐implant anchorage is better to be placed in the area with a distance of 5 mm from the alveolar crest .