The purpose of this study is to compare the effects and safety of Anlotinib with placebo in patients with Differentiated Thyroid Cancer.

Inclusion Criteria:

1. Signed and dated informed consent

2. Histological documentation of Differentiated Thyroid Cancer ,With measurable disease (using RECIST1.1)

3. ECOG PS:0-1,Life expectancy of more than 6 months

4. Subjects must be 131I-refractory / resistant as defined by at least one of the following:

   • Lesions that do not demonstrate iodine uptake on any radioiodine scan
   • Cumulative activity of 131I of >600 mCi or 22 gigabequerels (GBq)
   • Lesion that demonstrate iodine uptake on any radioiodine scan,but has progressed by RECIST 1.1 within 18 months of 131I therapy

5. main organs function is normal

Exclusion Criteria:

1. Prior treatment with Anlotinib or VEGFR-targeted therapies(such as Vandetanib,Cabozantinib,Lenvatinib,Sunitinib,Sorafenib etc.)
2. Subjects received radiotherapy external exposure or 131I within 3 months prior to the first dose of study drug or plan to be received any anti-cancer treatment during study
3. Patients suffering from other malignancies currently or within 5 years, except for cured cervical carcinoma in situ, non-melanoma skin cancers and superficial bladder cancer [ Ta (non-invasive carcinoma), Tis (carcinoma in situ) and T1 (carcinoma invasion into lamina propria) ]
4. CTCAE(4.0) Grade 1 or higher non-remission toxicity induced by any other previous treatments，excluding alopecia and Grade 2 or lower neurotoxicity induced by oxaliplatin
5. Patients with factors that could affect oral medication (such as dysphagia etc.)
6. Patients with pleural effusion or ascites, causing respiratory syndrome (CTCAE Grade 2 or higher dyspnea [Grade 2 dyspnea refers to Shortness of breath with a small amount of activities, affecting Instrumental activities of daily life])
7. Patients underwent major surgical treatment，open biopsy or significant traumatic injury within 28 days prior to assignment