Omohyoid muscle syndrome is rarely seen clinically. A mass can be seen on the neck while swallowing, and the patient feels discomfort and dysphagia. The mass disappears immediately after swallowing and you can't find the mass by palpation. We made autopsies in 50 cases of omohyoid muscle syndrome, and observed muscles, especially the intermediate tendons, sheaths of tendon and projection of omohyoid muscles. The restriction and regulatory functions of intermediate tendon sheaths during contraction of the omohyoid muscles were briefly explained. By combination with 2 cases of clinical reports, also investigated. We also investigated the etiology of omohyoid muscle syndrome.