The goal of this clinical trial is to evaluate the efficacy of Blinatumomab in pediatric patient with newly diagnosed acute B-Lymphoblastic leukemia with poor response to early chemotherapy, i.e. day 19 MRD ≥ 0.1% (low-risk) or day 19 MRD ≥ 0.01% (intermediate-risk). The main question is:

• If the flow cytometric MRD negative (<0.01%) rate and the NGS- MRD negative (<0.0001%) rate at the end of induction for patients received Blinatumomab will be superior to historical control (D46MRD in the CCCG-ALL2020 protocol).

Participants will:

• Take 14 days full dose Blinatumomab;
• With bone marrow evaluated before and after Blinatumomab treatment.

Inclusion Criteria:

• Age older than 1 month to younger than 18 years.
• Diagnosis of acute lymphoblastic leukemia by bone marrow morphology.
• Immunophenotyping: acute B-lymphoblastic leukemia;
• Meet one of the following situations:

A. Provisional low-risk: D19MRD ≥ 0.1%; B. Provisional intermediate-risk: D19MRD ≥ 0.01%;

• Subjects in the sytudy group or their guardians must be able to understand and accept the informed consent approved by the Ethics Committee

Exclusion Criteria:

• sIgM+;
• ALL evolved from chronic myeloid leukemia (CML);
• Down's syndrome, or major congenital or hereditary disease with organ dysfunction;
• Other secondary leukemias;
• CNS involvement;
• History of epilepsy; or convulsions within the last month;
• Known underlying congenital immunodeficiency or metabolic disease;
• Congenital heart disease with cardiac insufficiency;
• Treated with glucocorticoids for ≥14 days, or ABL kinase inhibitors for > 7 days within one month before enrollment, or any chemotherapy or radiotherapy within 3 months before enrollment (except for emergency radiotherapy to relieve airway compression);
• Initial diagnosis of high risk;
• D46MRD ≥1%.