Background: Blinatumomab has demonstrated its efficacy and safety in pediatric patients with B-cell acute lymphoblastic leukemia (B-ALL). Methods: We enrolled patients aged 0-18 years who were diagnosed with CD19-positive B-ALL and treated with blinatumomab between January 2021 and May 2023 from 14 centers in China. Results: A total of 304 patients were enrolled in this analysis. In the patients with ＞5% blasts before blinatumomab (non-complete remission, NCR group), 75.9% achieved complete remission (CR) and 69.0% achieved minimal residual disease (MRD) negativity. Among the patients with ≤5% blasts but multiparametric flow cytometry MRD (MFC-MRD) positive (MRD+ group), 98.9% achieved MRD negativity. Of the MFC-MRD negative patients (MRD- group), the quantitative polymerase chain reaction MRD (qPCR-MRD) and next-generation sequencing MRD (NGS-MRD) clearance rate was 60.0% and 65.5%, respectively. Additionally, Patients in the MRD+ and MRD- groups had significantly better outcomes than those in the NCR group, with 30-month overall survival (OS) rates of 95.3% (95% CI: 91.4-99.3%), 91.2% (95% CI: 85.0-97.8%), and 77.6% (95% CI: 67.4-89.4%), respectively (P<0.001), and 30-month event-free survival (EFS) rates of 93.9% (95% CI: 89.6-98.3%), 90.8% (95% CI: 85.0-97.1%), and 56.7% (95% CI: 41.0-78.6%), respectively (P<0.001). In this study, 41.4% of patients experienced grade ≥3 adverse events (AEs), with hematological toxicity being the most common (33.2%). The severe adverse events, such as cytokine release syndrome (CRS) and neurotoxicity, occurred at a low rate, particularly grade ≥3, at 3.6% and 2.6%, respectively. Conclusions: Overall, these results indicate that blinatumomab is effective and well-tolerated. Patients with a lower leukemia burden before blinatumomab administration tend to have better OS and EFS with fewer AEs.