Inclusion Criteria:

          1. Aged 18-70 years;

          2. Eastern cooperative oncology group (ECOG) performance status of 0 to 2;

          3. Life expectancy≥12 weeks;

          4. CD19 tumor expression demonstrated in bone marrow or peripheral blood by flow
             cytometry;

          5. Relapsed or refractory B- ALL: a) Refractory B- ALL: Fail to achieve a CR after 2
             cycles of a standard induction chemotherapy regimen or one-line/multi-line salvage
             chemotherapy; b) Relapsed B- ALL: Relapse after remission for the first time in 12
             months or relapse after one-line/multi-line salvage chemotherapy; Relapse is defined
             as recurrence of primitive cell in peripheral blood or bone marrow(>5%) after
             remission; c)Relapse after autologous stem cell transplantation or allogeneic
             hematopoietic stem cell transplantation; d)Patients with Philadelphia chromosome
             positive(Ph+) ALL were eligible if they were intolerant to or had failed two lines of
             tyrosine kinase inhibitor (TKI) therapy, or had t315i mutation.

          6. Did not receive hematopoietic stem cell transplantation≤6 months prior to enrollment;

          7. Adequate organ function defined as: a) Creatinine clearance (as estimated by Cockcroft
             Gault method) >60 mL/min; b) Serum ALT/AST <2.5 ULN; c) Total bilirubin <1.5 ULN
             (subjects with Gilbert's syndrome≤3 ULN); d) Cardiac ejection fraction≥50%, no
             evidence of clinically significant pericardial effusion as determined by an ECHO; e)
             No clinically significant pleural effusion; f) Baseline oxygen saturation >92% on room
             air;

          8. Females of reproductive age must be in non-lactation period. Females of childbearing
             potential must have a negative serum or urine pregnancy test. All subjects must use
             medical-approved-contraception (such as intrauterine device and contraceptive drugs)
             during the treatment and in 2 years after cell transfusion treatment; Males should
             avoid sperm donation;

          9. Venous access can be established, peripheral blood mononuclear cells (PBMC) can be
             collected in researcher's judgement;

         10. The subject agrees to and sign informed consent form;

         11. The subject can communicate well with the researcher, is willing and able to comply
             with the research plans, and finish the research according to the research rule.

        Exclusion Criteria:

          1. Isolated extramedullary leukemia or isolated extramedullary disease relapse;

          2. Central nervous system leukemia involved CNS3;

          3. Concomitant malignancy other than cured non-melanoma skin cancer or cervical carcinoma
             in situ or localized prostate cancer or superficial bladder cancer or ductal carcinoma
             in situ or diagnosis of other malignancy exceeds 5 years without relapse or treatment
             during the 5 years;

          4. Any result of the following infectious disease tests is positive: HIV; HCV; HBsAg; or
             HBcAb positive with HBV DNA copies positive; TPPA;

          5. Live vaccine ≤4 weeks prior to enrollment;

          6. For Ph+ ALL, TKI therapy ≤1 week prior to enrollment;

          7. History of anti-CD19 therapy or CAR-T or other gene-editing T cell therapy;

          8. Presence of ≥ grade 2 acute graft-versus-host disease (GVHD, Glucksberg criteria) or
             extensive chronic GVHD (Seattle criteria) that require treatment ≤4 weeks prior to
             enrollment, or during the study period the subject is required to receive anti-GCHD
             therapy in researcher's judgement;

          9. Presence of concomitant disease that require systemic steroids or other immune
             suppressive therapy during the study period in researcher's judgement; Allogeneic cell
             therapy (such as donor lymphocyte infusion, DLI) ≤4 weeks prior to enrollment;

         10. CNS stereotactic radiotherapy ≤4 weeks prior to enrollment;

         11. Toxicities related to previous therapy did not relieved to ≤1 grade, except
             hematological toxicity and alopecia;

         12. Known life-threatening hypersensitivity to cyclophosphamide or fludarabine, or
             presence of other intolerant conditions, or severe allergic constitution;

         13. Patients with active autoimmune disease (e.g., systemic lupus erythematosus, sjogren
             syndrome, rheumatoid arthritis, psoriasis, multiple sclerosis, inflammatory bowel
             disease, Hashimoto's thyroiditis, hypothyroidism which can be controlled by thyroid
             hormone replacement therapy is an exception);

         14. For patients that underwent or plan to undergo major surgical operation before CAR-T
             treatment, major surgery which required general anesthesia happened ≤4 weeks prior to
             enrollment, or did not be fully recovered and clinically stable prior to enrollment,
             or be anticipated to undergo major surgical operation which requires general
             anesthesia during the study;

         15. Took drug from other research≤28 days prior to enrollment;

         16. Any unstable cardiovascular diseases happened ≤6 months prior to enrollment, including
             but not limited to, unstable angina, myocardial infarction, heart failure (NYHA grade≥
             III grade), severe arrhythmia that require drug interference, cardiac
             angioplasty/coronary stent implantation/ cardiac bypass surgery ≤6 months prior to
             enrollment;

         17. Presence of central nervous system (CNS) disease or disease history, including
             epilepsy, cerebral ischemia/bleeding, dementia, cerebellar disease, or any autoimmune
             diseases that involve CNS;

         18. Any other condition that researcher think it is inappropriate for the subject to
             anticipate the trial.