Chronic Graft-versus-host disease (GVHD)， with the incidence of 30%-60%, is a serious late complication of allogeneic hematopoietic stem cell transplantation (HSCT) and is the major cause of death in the late stage of transplantation. According to targeted organs, cGVHD is divided into two types, limited cGVHD and extensive cGVHD. Extensive cGVHD needs systemic immunosuppressant treatment. However, currently standard first-line regimen including cyclophosphamide and prednisolone is only effective for some patients. Novel treatment is urgently needed. Our previous study has shown that mesenchymal stem cells (MSCs) are effective for cGVHD patients with multiple skin damage. To further explore the therapeutic effect of MSCs for extensive cGVHD, we plan to conduct a multi-center clinical trial. Patients who developed an extensive cGVHD (with skin and/or liver damage) after HSCs transplantation and do not respond to first-line therapy are enrolled. They will be randomly divided into two groups which will receive MSCs and routine second-line drugs respectively. We will evaluate the efficacy and safety of MSCs for extensive cGVHD by comparison of symptom improvement, survival rate, recurrence as well as side effects in the two groups.