This is case report of true class III malocclusion with macroglossia is corrected by glossectomy in 13 years female patient. After orthodontic treatment, the patient is bound to glossectomy because the corrected condition is relapsed to the previous condition due to relatively enlarged tongue compared with the original dental arch. By the interpretation of the cephalogram and model analysis, it is approved that the growth pattern and direction are normal range and mandible is located anterioly to the cranium. The results are follows: 1. We could treat the true Cl III malocclusion. 2. We could prevent the relapse of the treated condition by the surgical intervention, such as partial glossectomy. 3. Sensory, speech, swallowing and so other functions after the operation have been with in normal limit without any serious complications or seguellae.