This prospective multicenter study evaluates the efficacy and safety of PD-1 inhibitor combined with venetoclax and HAG/CAG chemotherapy in refractory/relapsed T-ALL (R/R T-ALL). Despite standard chemotherapy, R/R T-ALL remains challenging, with low salvage remission rates (\~40%) and poor survival. Preclinical data suggest PD-1 blockade enhances leukemic stem cell eradication, while venetoclax (BCL-2 inhibitor) synergizes with chemotherapy. Eligible patients receive 1-2 cycles of PD-1 inhibitor + venetoclax + CAG, with responders proceeding to allo-HSCT or MRD-guided consolidation. The trial aims to improve CR rates and survival, offering a novel immunochemotherapy approach for this high-risk population.