Objective:Comparison of conventional chemotherapy and immunotargeted therapy efficacy in patients with relapsed/refractory (R/R) acute B cell leukemia (B-ALL) .Methods:The clinical data of 212 patients with R/R B-ALL in the Affiliaed Cancer Hospital of Zhengzhou University from January 2008 to July 2020 were analyzed retrospectively to compare the response rate and survival time difference between conventional chemotherapy and immunotargeted therapies (antiCD19 CAR-T and CD3CD19 bi-specific antibody blinatumomab) , and to explore the related factors affecting prognosis.Results:The CR rate of patients with R/R B-ALL treated with anti-CD19 CAR-T cells was 80.4% , patients treated with blinatumomab was 62.5% , and patients treated with chemotherapy was 38.6% . There was significant difference in the CR rate among the three therapies ( P<0.001) . CAR-T cells 1-year OS rate was 41.5% , which was significantly higher than that of the chemotherapy group (10.3% ) ( P<0.001) . The 1-year PFS rate of CAR-T cells (30.1% ) was also significantly higher than that of the chemotherapy group (9.7% ) ( P<0.001) . The median OS of patients with bridging allo-HSCT after CR treatment by CAR-T cells was 18.5 months, which was higher than that of patients without allo-HSCT (8 months) ( P=0.027) . The median PFS of patients with allo-HSCT was 17 months, which was higher than that of patients without allo-HSCT (4 months) ( P=0.001) . The 1-year OS rate of patients treated with blinatumomab was 14.3% , which was higher than that of the chemotherapy group (10.3% ) ( P=0.018) . The 1-year PFS rate (14.6% ) was also higher than that of the chemotherapy group (9.7% ) ( P=0.046) . The median OS and median PFS of patients with bridging allo-HSCT were 13 and 11 months, respectively, which was higher than that of patients without allo-HSCT (9.5 and 6 months) . The cytokine release syndrome (CRS) incidence in patients with R/R B-ALL treated with anti-CAR-T cells was 89.8% . Grades 3-4, grade 2, and grade 1 CRS were experienced by 30.2% , 11.3% and 58.5% patients, respectively. Only three patients (37.5% ) with blinatumomab developed CRS, all of which were grade 1. Conclusion:The response rate and survival rate of patients with R/R B-ALL treated with CD19 CAR-T cells and blinatumomab were significantly better than those treated with conventional chemotherapy.