Inclusion Criteria:
* Patients with thymoma or thymic carcinoma confirmed by cytologically or histologically (WHO Classification of Thoracic Tumors 5th ed), including all pathological subtypes;
* Patients with advanced recurrent, unresectable and/or metastatic thymic tumor as defined by the Masaoka-Koga stage;
* Subsequent relapse of disease following first-line systemic chemotherapy;
* Patients with at least one measurable lesion as defined by RECIST V1.1; Measurable lesions located within the radiation field of previous radiotherapy or after local treatment can also be selected as target lesions if progression is confirmed.
* Eastern Cooperative Oncology Group performance status score of 0 or 1;
* Life expectancy \> 12 weeks;
* Adequate organ and marrow function;
* Patients should participate in the study voluntarily and sign informed consent.
Exclusion Criteria:
* Patients with thymus neuroendocrine tumors;
* Any patient who is known to have central nervous system (CNS) metastasis or imaging shows a risk of CNS metastasis;
* Previous (within the last 5 years) or current malignancies at other sites;
* Gastrointestinal abnormalities;
* Cardiovascular and cerebrovascular diseases;
* Patients who have previous treatment with small molecule VEGFR-TKI (except patients whose treatment cycle is less than 2 weeks due to intolerance or other reasons); Patients who have previous treatment with PD-1 / PD-L1 antibody combined with small molecule VEGFR-TKI;
* Involved in other clinical trials within 4 weeks before enrollment; Prior anti-tumor therapies with chemotherapy, cytotherapy, immunotherapy, operation (Interventional therapy excepted) within 4 weeks 4 weeks before enrollment; Prior radiotherapy (palliative radiotherapy excepted) within 2 weeks; Prior small-molecule targeted therapy within 2 weeks or 5 half-lives.
* Presence of unresolved toxicities from prior anti-tumor therapy, defined as having not resolved to NCI CTCAE V5.0 grade 0 or 1 with the exception of alopecia;
* Skin wound, surgical site, wound site, mucous membrane severe ulcer or fracture comfirmed as having not recovered;
* Uncontrolled mass pleural effusion, ascites, and pericardial effusion;
* Active autoimmune diseases: Myasthenia gravis, pure red cell aplastic anemia, systemic lupus erythematosus, inflammatory bowel disease, etc;
* Need immunosuppressive agents or hormone therapy for immunosuppression, , and still need immunosuppressive therapy within 2 weeks before enrollment;
* Active bacterial, viral or fungal infection; Fever of unknown cause (\> 38.5℃) occurred within 2 weeks before enrollment;
* Patients who are positive for both Hepatitis B surface antigen (HBsAg) and hepatitis B virus deoxyribonucleic acid (HBV-DNA) quantification results; Patients who are positive for both hepatitis C virus antibody (HCAB) and hepatitis C virusribonucleic acid (HCV-RNA) quantification results; Patients who are positive for human immunodeficiency virus (HIV);
* Pregnant or lactating women;
* Patients who do not take contraception during the study period and within 6 months after the study;
* Patients with insufficient compliance as evaluated by investigator;
* The investigator believes that it is not suitable to patient in this clinical trial.
