Adenoid cystic carcinoma (ACC), which occurs in the salivary glands of oral and maxillofacial tissues, accounts for about 10% of all salivary gland tumors and can also occur in the lacrimal gland, skin, breast, external auditory canal, lung, prostate, cervix and other parts of the body. Among the epithelial-derived malignancies of salivary glands, ACC occupies the second place after mucous epidermis-like carcinoma, and some scholars have reported that it is the first among small salivary gland malignancies. ACC has a slow growth, low local lymphatic metastasis rate, easy recurrence and distant metastasis, and early neurological invasion. Therefore, ACC has been described as one of the most devastating and unpredictable tumors of the head and neck. Based on the biological characteristics of ACC, its treatment is currently based on surgical enlargement. However, because of its early local infiltration, which is often indistinguishable to the naked eye, and its neuroinvasive nature, primary resection is often difficult to reach a safe margin, so a combination of surgery with postoperative radiation therapy is often used. Traditionally, adenoid cystic carcinoma of the small salivary gland was classified as insensitive to radiotherapy, but with the rapid development of modern radiotherapy medicine, many scholars have found that the combination of surgical treatment and postoperative radiotherapy for adenoid cystic carcinoma of the small salivary gland is significantly more effective than surgery alone.