Objective： To evaluate the clinical effect and safety of periodontal-orthodontic treatment in patients with aggressive periodontitis (AgP) and malocclusion. Methods: A retrospective analysis was conducted in 25 AgP patients, who had received periodontal-orthodontic treatment in Peking University School and Hospital of Stomatology. Clinical indexes, including probing depth (PD), bleeding index (BI) and percentage of sites with bleeding on probing (BOP%) were evaluated at three time points: Baseline (T0); active periodontal treatment finished and before orthodontic treatment (T1); and after orthodontic treatment (T2). Also changes of ratio of the residual alveolar bone height (RBH) and the occurrence of root resorption were evaluated by periapical radiographs. Results: (1) Compared with T0, all the clinical parameters including PD, BI, BOP% and percentage of sites with PD>3 mm were significantly improved (P<0.001). (2) Significant difference was observed in the average RBH between T0 (68.37%±15.60% and T2 (70.27%±14.23%). RBH in upper incisors ［(58.79%±16.71% at T0, 65.54% (55.74%, 78.13%) at T2］, upper canines ［77.62% (66.06%, 87-17%) at T0, 79.57% (69.75%, 86.52%) at T2］ and upper molars ［74.30% (61-69%, 84-45%) at T0, 76.76% (68.12%, 85.09%) at T2］ showed significant increase (P<0.05). (3) After orthodontic treatment, varying degrees of root resorption occurred in (23.94%±13.45%) of teeth per capita, among which the lower and upper incisors showed the highest incidence (68.48% and 65.31% in homogeneous teeth, respectively). Conclusion: After active periodontal treatment, orthodontic treatment in AgP patients had not aggravated inflammation and alveolar bone resorption; root resorption occurred in two-thirds of incisors approximately.