Precursor B cell acute lymphoblastic leukemia (B-ALL) is an aggressive type of leukemia, with high relapse rate and poor long term survival in adults. Traditional treatment regimens mainly include chemotherapy and hematopoietic stem cell transplantation. In the past decade, with the application of molecular targeted drugs and immunotherapy, the survival of B-ALL patients has significantly improved. In this study，we propose a treatment approach that combines Blinatumomab and Reduced-dose Chemotherapy in B-ALL adults. Our study aims to answer the safety and efficacy of this treatment regimen, and further improve the survival for those participants.