The causes of painful submandibular lymph node swelling include infectious diseases, immune system diseases, malignant tumors, etc., which need to be diagnosed in time to clarify the cause of the disease and be treated according to the doctor’s instructions. 1. Infectious diseases: including oropharyngeal infections, such as acute suppurative tonsillitis, gingivitis, pharyngitis, etc., inflammation involving submandibular lymph nodes will lead to swelling and pain; thyroid diseases, such as thyroiditis, etc.; lymph node tuberculosis. Various infectious diseases of the oropharynx and neck can lead to submandibular lymphadenitis, and these lymph nodes are painful and tender with good mobility. 2. Immune system diseases: such as systemic lupus erythematosus, dermatomyositis, autoimmune lymphoproliferative syndrome and so on. These diseases result in enlarged submandibular lymph nodes, sometimes with pain or compression symptoms. 3. Malignant tumors. A variety of malignant tumors may present with submandibular lymph node metastasis, such as nasopharyngeal cancer, breast cancer, lung cancer, etc.; hematologic tumors, such as leukemia, malignant lymphoma, etc.. The enlarged lymph nodes caused by these diseases are usually painless, hard and poorly movable, and may be painful when accompanied by compression of surrounding tissues, etc. The presence of painful submandibular lymph node enlargement, need to actively consult the doctor, improve the examination, clear diagnosis and follow the doctor’s instructions for treatment.