Adenoid cystic carcinoma is a common malignant tumor of the salivary gland, and its incidence ranks second among malignant tumors of the salivary gland. Adenoid cystic carcinoma is highly malignant, locally infiltrative and invasive, and can easily grow along the nerves and spread into the skull. The field of oncology describes adenoid cystic carcinoma as “the most difficult tumor to treat” and as “one of the most biologically devastating and unpredictable head and neck tumors”. The treatment principle for adenoid cystic carcinoma is surgical resection + post-operative radiotherapy, while radical radiotherapy is used for those who cannot undergo surgery or refuse surgery. The target area of adenoid cystic carcinoma radiation therapy should include the pathways of the nerves innervated by the lesion, i.e., “root tracing target area of the involved nerves”.