B-ALL patients received regular follow-up after allogeneic hematopoietic stem cell transplantation, and in case of recurrence, they were given Blinatumomab. Anti-treatment was followed by DLI, and the second course was performed 1-2 months after DLI. Patients with positive MRD were treated with Blinatumomab 28μg×5-15 days, followed by DLI treatment. (MNC infusion is about 5×10\^7/kg\ 1×10\^8/kg). Patients with hematologic recurrence were given Blinatumomab 9μg D1-4,11.66μg d5-7,28μg Starting from d8 （8 to 21 days in total）, followed by DLI treatment (infusion of MNC approximately 5×10\^7/kg\ 1×10\^8/kg). Objective To observe and analyze the efficacy and side effects of Blinatumomab followed by donor lymphocyte infusion in patients with relapsed acute B lymphoblastic leukemia after allogeneic hematopoietic stem cell transplantation in our hospital.