In this study, CAR-T will be administered to children with acute lymphoblastic leukemia to explore the effect of CAR-T intervention time on the duration of complete remission and further verify the long-term safety and efficacy of CAR-T treatment.

After clinician evaluation, if the child meets the study criteria and after adequate communication, the parent or legal guardian voluntarily joins the clinical study, CAR-T technique can be used for related treatment, and the long-term therapeutic effect can be observed. In this trial, 50 children were publicly enrolled and treated with CAR-T. Patients participating in the clinical trial will be tested and assessed in terms of treatment safety, efficacy, and duration of response.

Inclusion criteria：

1. The treat history meeting the following criteria:

   Recurrence of lymphoma patients with imaging (CT/MRI/PET-CT) detection and pathological diagnosis, or recurrence including bone marrow morphology relapse and the MRD recurrence of myeloma patients or leukemia patients, after chemotherapy or stem cell transplantation; Can't get complete remission (including MRD positive) after more than twice repeated chemotherapy of incipient lymphoma, myeloma or leukemia patients; One or twice chemotherapy cannot get remission again (including MRD positive), but not suitable for chemotherapy of incipient lymphoma, myeloma or leukemia patients.

2. There is a measurable lesions before treatment at least;

3. ECOG score≤2;

4. To be aged 1 to 18 years;

5. More than a month lifetime from the consent signing date

Exclusion Criteria:

1. Serious cardiac insufficiency, left ventricular ejection fraction<50%;
2. Has a history of severe pulmonary function damaging;
3. Merging other progressing malignant tumor;
4. Merging uncontrolled infection;
5. Merging the metabolic diseases (except diabetes);
6. Merging severe autoimmune diseases or immunodeficiency disease;
7. Patients with active hepatitis B or hepatitis C;
8. Patients with HIV infection;
9. Has a history of serious allergies on Biological products (including antibiotics);
10. Has acute GvHD on allogeneic hematopoietic stem cell transplantation patients after stopping immunosuppressants a month;
11. Any situation that would increase dangerousness of subjects or disturb the outcome of the clinical study according to the researcher's evaluation.