Inclusion Criteria:  1. Understood and signed an informed consent form. 2. ≥12 years old, Karnofsky Performance Scale of ≥60, life expectancy ≥ 6 months.  3. Has received allogeneic hematopoietic stem cell transplantation (alloSCT). 4. Clinically diagnosed moderate to severe cGVHD according to NIH Consensus Criteria.  5. Has received systemic or topical corticosteroids therapy and confirmed steroid-refractory/dependent cGVHD according to NIH Consensus Criteria.  6. Has received at least 1 lines of therapy for cGVHD. 7. Adequate laboratory indicators. 8. No pregnant or breastfeeding women, and a negative pregnancy test.  Exclusion Criteria:  1. Has active acute GVHD. 2. Has previously failed to respond to JAK inhibitors for GVHD, or who had used JAK inhibitors within 4 weeks before the first administration.  3. Has uncontrollable active infections or infections requiring systematic treatment within 7 days before the first administration.  4. Development of other basic diseases. 5. Has malignant tumors within 3 years. 6. Has multiple factors affecting oral medication. 7. Has substance abuse or a psychotic disorder. 8. Has severe and / or uncontrolled disease. 9. Allergic to drugs or its constituents. 10. Has participated in any other clinical trials within 4 weeks before first administration.  11. According to the judgement of the investigators, there are other factors that may lead to the termination of the study.