Background:Chimeric antigen receptor T-cells (CAR-T) targeting CD19 therapy is reported to induce 83-93% response in relapsed/refractory acute lymphoblastic leukemia (r/r-ALL) in adults. However, 30-60% of patients relapse after CAR-T treatment, of which 14-25% CD19-negative relapse. In spite of CAR-T cells persistence, CD19 absent causing tumors that evade CAR-T cells mediated recognition and clearance. For CD19-negative relapse, it is necessary to explore more effective targets. There are some research proved that compared with single-targeted CARs, CD19/CD22 dual-targeted CARs induce more IFN-γ and IL-2 in vitro and eradicate patient-derived xenografts (PDX) produced with CD19-negative relapse of CD19-directing CAR-T treatment. Therefore, our study explored the efficacy and safety of clinical studies on mixture of CD19 CAR-T and CD22 CAR-T cells in the treatment of r/r ALL in adults.