To compare the efficacy of donor derived CD19 car T cells and chemotherapy plus donor lymphocyte infusion in the treatment of recurrent CD19 positive B-ALL...The rates of complete remission (77.3%) in the CAR-T group were significantly higher than those in the Chemo- DLI group (38.1%) ; The 1- and 2-year leukemia-free survival(LFS) in the CAR-T group and Chemo-DLI group were 54.5% vs 9.5%, 45.5% vs 4.8% , respectively. The 1- and 2-year overall survival(OS) in the CAR-T group and Chemo-DLI group were 68.2% vs 19% , 63.6%vs 9.5%, respectively. Compared with chemotherapy plus DLI, donor-derived CD19 CAR-T is more effective and safe in the treatment of recurrent B-ALL...