This study is a multicenter, open-label, phase II study to evaluate the efficacy and safety of Benmelstobart in combination with Anlotinib as a second-line treatment for locally advanced or metastatic differentiated thyroid cancer. Patients who meet the inclusion criteria and do not meet the exclusion criteria will receive Benmelstobart (1200mg, d1, q3w) in combination with Anlotinib (12mg, qd, d1-14, q3w). Treatment will continue until disease progression, voluntary withdrawal of informed consent, intolerable toxicity, or until the investigator determines that the patient no longer benefits. For locally advanced patients, if the disease converts from unresectable or borderline unresectable to resectable after treatment, surgical intervention will be performed.