Temporomandibular disorder (TMJ) is a common disease in dentistry, among which temporo mandibular disorder (TMD) is particularly common. With the development of China’s economic level and the general improvement of culture, the demand for TMJ diagnosis and treatment is also increasing. Then it is necessary to understand the structure of our TMJ and what is TMD. The temporomandibular joint (TMJ) consists of the articular fossa of the temporal bone, the condyle of the mandible, the articular disc between them, and the surrounding neurovascular and connective tissues. — chewing, swallowing, speech …… The incidence of TMD is high, and there is no consensus on its etiology and treatment. The TMJ is located on both sides of the head and is a linkage joint. The TMJ is closely related to the occlusion of the maxillofacial muscles and teeth, and muscle lesions or occlusal disorders can affect the TMJ to some extent. Changes in the function of the maxillofacial muscles will also have an impact on the function of the TMJ. The condylar cartilage in the TMJ is subject to lifelong modification within the limits of its capacity, but if the normal masticatory movement (clenching or grinding) does not occur, it will affect the dentition and periodontal tissues, and at the same time cause damage to the TMJ, damaging the normal anatomical structures in the TMJ, thus causing TMD.