Safety and Efficacy Evaluation of IM19 CAR-T Cells (IM19CAR-T)

Inclusion Criteria: 1. Patients with CD19+ Refractory or Relapsed B-ALL（At least 2 prior combination chemotherapy regimens） 2. To be aged 3 to 75 years 3. Blast in blood ≤ 30% 4. ECOG score ≤2 5. Women of childbearing potential must have a urine pregnancy test taken and proven negative prior to the treatment. All patients agree to use reliable methods of contraception during the trial period and until follow-up for the last time. 6. Voluntary participation in the clinical trials and sign the informed consent. Exclusion Criteria: 1. Intracranial hypertension or unconsciousness 2. Respiratory failure 3. CD19 negative 4. Disseminated intravascular coagulation 5. ALT /AST\>3 x normal value; Creatinine\> 1.5 x normal value; Bilirubin \>2.0 x normal value 6. Hematosepsis or Uncontrolled active infection 7. Uncontrolled diabetes 8. Abalienation; 9. WHO Sscore \>3 10. Patients in pregnancy or breast-feeding period 11. Previously treatment with any gene therapy products 12. Any uncontrolled medical disorders that the researchers consider are not eligible to participate the clinical trial 13. Any situation that would increase dangerousness of subjects or disturb the outcome of the clinical study according to the researcher's evaluation.