Donor-derived CD19-directed chimeric antigen receptor-modified T (CAR-T) cell therapy seems be effective and safe for relapsed B-ALL after allogeneic haematopoietic stem cell transplantation (allo-HSCT). We report two cases of children who received Donor-derived CAR-T cell therapy. After transfusion, the children experienced different degrees of chronic graft-versus-host disease (cGVHD). Early intervention included strengthening immunosuppressant, FAM regimen, tyrosine kinase inhibitor, and auxiliary cell therapy. Their dyspnoea and lung function were significantly improved and recovered. They did not receive the second transplant. Timely and effective intervention is crucial to improve both prognosis and quality of life.