The patient was a 22-year-old male admitted to the hospital with the main reason of a painless swelling on the left side of the neck for 1 month. 1 month ago he was found by others to have an enlarged left side of the neck without any symptoms and the mass sometimes showed large and sometimes small. The clinical examination showed good general condition. The specialist showed an enlarged left side of the neck with normal surface skin color and a soft mass on palpation with no clear border. CT examination showed a deep surface of the left submandibular gland, down to the plane of thyroid cartilage 4×7×4 cm mass with irregular shape and clear borders. It was cystic in nature. Treatment history: routine examination after admission and no contraindication to surgery was found. Surgical procedure: An incision was made on the left side of the floor of the mouth along the surface of the sublingual gland in the maxillo-lingual sulcus, the sublingual gland was separated along the surface of the sublingual gland, the ducts of the submaxillary gland and the lingual nerve were avoided, the sublingual gland was gradually separated and removed, and the cystic mass on the floor of the mouth was removed by submaxillary incision. The wound was healed in one stage. There was no recurrence at 1 year postoperative follow-up.