1.Periodontal preparation before orthodontic treatment: Ask the periodontist to do periodontal evaluation and technical treatment, and orthodontic treatment must be carried out only when the periodontal condition is under control, otherwise it is easy to cause rapid irreversible periodontal damage. 2.Improve patients’ periodontal protection: Before orthodontic treatment, patients must be informed of their condition, the severity of the disease and the precautions to be taken during treatment, and explain how to maintain periodontal health. 3, periodontal treatment in orthodontic treatment to reduce plaque accumulation and eliminate gingival inflammation: (1) Adopt orthodontic appliances with simple structure and composition (2) Review in periodontal department every 3 months during orthodontic treatment for comprehensive assessment of periodontal status: including depth of periodontal pockets, bleeding on probing, tooth movement, amount of gingival recession, level of alveolar bone, etc., and make timely treatment according to the situation. Orthodontic treatment may be terminated if necessary. (3) Comprehensive and careful scaling is required before orthodontic depression of elongated teeth. Avoid changing the supragingival plaque into subgingival plaque in the process of depressing the teeth, leading to the aggravation of periodontal disease. 4, orthodontic treatment in the force control: due to the loss of supporting bone, periodontal membrane area is reduced, the same orthodontic force on the affected teeth to produce a unit area of pressure than normal teeth. Therefore, the absolute orthodontic force value should be reduced as appropriate for teeth with periodontal disease to prevent damage to the periodontal membrane, dental bone and alveolar bone, especially to prevent accelerated resorption of alveolar bone. 5, orthodontic treatment for patients with periodontal disease must be adjusted to remove the early contact point: periodontitis patients with varying degrees of alveolar bone resorption, tooth loosening, under the combined force, prone to tooth misalignment, poor occlusal relationship, etc., thus aggravating the process of periodontal disease, so in the orthodontic treatment of periodontal disease to maintain a normal occlusal relationship is the key to maintain the functional physiological stimulation of periodontal health, adjustment is the key to orthodontic treatment and The aim is to eliminate early contact and coaptation. The aim is to eliminate early contact and coincidental interference.