The periodontal ligament is a connective tissue located between the cementum that covers the roots of the tooth and alveolar bone, which is composed of large amounts of fibers, cells, and blood vessels. Orthodontic tooth movements are obtained through periodontal ligament remodeling and alveolar bone in response to orthodontic forces. When the orthodontic force is applied to the teeth, an injury will occur in the periodontal ligament, and the pressure and tension side in the periodontal ligament is formed. Furthermore, vasoconstriction occurs in blood vessels and hypoxia in the periodontal ligament, triggering inflammation, angiogenesis, cell proliferation, degradation, and synthesis of extracellular matrix, bone resorption, and alveolar bone deposition. The purpose of this article is to study the mechanism of periodontal ligament remodeling on orthodontic tooth movement to obtain optimal tooth movements.