The clinical data of one patient with severe mesioclination impaction of bilateral mandibular second molars were collected. Combined with literature review， the orthodontic clinical scheme for the treatment of this kind of patient was discussed.

One 21-year-old female patient with severe mesioclination impaction of bilateral mandibular second molars with crowded dentition was diagnosed as Angle Class Ⅱ malocclusion， Mao Ⅰ¹+Ⅲ¹+Ⅴ malocclusion and skeletal Class Ⅰmalocclusion.After extraction of 15， 18， 28， 38 and 48， the micro-implants were implanted in the front edge of bilateral mandibular ramus. After surgical exposure of bilateral mandibular second molars， the mandibular second molars were uprighted by using the traction of elastic rubber line between the micro-implant and the lingual buckle of surface of the second molars. After the orthodontic treatment， a good occlusal relationship was established between the mandibular second molar and the opposite teeth， and a good adjacent relationship was built up with the mandibular first molar.

For the patients with severe mesioclination impaction of mandibular second molars， the micro-implants can provide anchorage for the orthodontic treatment， and concisely and efficiently achieve a good occlusion and abutment relationship.