The currently CAR-T cell therapy in clinical practice largely depends on the expansion of CAR-T cells in vivo. However, the in vitro preparation process of CAR-T cells is complex and costly. In vivo CAR-T cell therapy eliminates the need for ex vivo preparation, significantly reducing treatment costs and procedural complexity. It enables immediate use, thereby improving patient accessibility. CD19 is stably overexpressed in more than 90% of B-cell malignancies. BAFF plays a core regulatory role in the survival, maturation, and homeostasis maintenance of B cells. BAFF-R is selectively expressed on the surface of mature B cell subsets and most B-cell malignancies. Currently, BAFF-R-based CAR-T therapy is in preclinical and early clinical research stages, demonstrating promising therapeutic potential, particularly offering a novel treatment option for patients with CD19-negative or drug-resistant B-cell tumors. The use of CD19/BAFF-R in vivo CAR-T cells as a new anti-tumor therapy may provide a new research direction for the treatment of relapsed/refractory B-cell acute leukemia/malignant lymphoma.