ion cyclophosphamide (PTCy) in haploid hematopoietic stem cell transplantation in children with thalassemia. Methods The clinical data of 28 children with thalassemia who received haploid hematopoietic stem cell transplantation were retrospectively analyzed. All children received regimen of busulfan+cyclophosphamide+fludarabine+anti⁃human thymocyte globulin (ATG) combined with PTCy+mycophenolate mofetil+cyclosporin to prevent GVHD. The transplantation effect, GVHD occurrence, infection and death, overall survival rate, and event⁃free survival rate were evaluated in children. Results (1) The median values of CD34+ cell number, total nucleated cell number, and mononuclear cell number were 11.2×106/kg, 17.6×108/kg, and 5.1×108/kg in graft of 28 children, with the engraftment success rate of 100%, and the median time of neutrophil engraftment was 14 days and 24 days for platelet engraftment, respectively. The incidence rate of engraftment dysfunction was 7.1%. (2) The incidence rate of GVHD was 28.5%, therein the incidence rates of acute GVHD in types Ⅰ-Ⅱ and Ⅲ-Ⅳ were 7.1% and 14.3%, respectively, and the incidence rate of chronic GVHD was 7.1%. (3) The incidence rate of cytomegalovirus infection, Epstein⁃Barr virus infection, and fungal infection were 64.3%, 10.7%, and 21.4%, respectively, and 2 children (7.1%) were dead in total; moreover, the 3⁃year overall survival rate and 3⁃year event⁃free survival rate were all 92.9% in children. Conclusion For children with thalassemia undergoing haploid hematopoietic stem cell transplantation, busulfan+cyclophosphamide+fludarabine+ATG combined with PTCy+mycophenolate mofetil+cyclosporin regimen is a choice of relatively high safety that can effectively decrease the post⁃transplantation GVHD incidence rate, and dose not affect engraftment effect. However, complications such as infection after transplantation are still serious clinical problems, and more optimized regimens need to be explored.