This is a multi-center, phase I trial that studies the efficacy and recommended dose of BCMA CART cells in treating patients with BCMA-positive multiple myeloma (MM) that have not respond or relapsed after chemotherapy. B-cell maturation antigen (BCMA), a cell surface protein expressed on malignant plasma cell, has emerged as a very selective antigen to be targeted in novel immunotherapy for MM.

Inclusion Criteria:

• 1. ≥ 18 years of age at the time of signing informed consent;

• 2. Cytology or tissue biopsy meets diagnostic criteria for multiple myeloma (according to IMWG criteria);

• 3. Bone marrow specimens confirmed positive BCMA expression in plasma cells and myeloma cells by immunohistochemistry or flow cytometry (>5%);

• 4. Have measurable disease by International Myeloma Working Group (IMWG) criteria based on one or more of the following findings:

  • Serum M-protein≥ 1 g/dL（≥10 g/L）
  • Urine M-protein ≥ 200 mg/24 hour
  • Involved serum free light chain (FLCs) level≥10 mg/dL with FLCs abnormal ratio (<0.26或>1.65)

• 5. Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1;

• 6. Diagnosis of MM with relapsed or refractory disease and have had at least 1 prior lines of therapy.

Exclusion Criteria:

• 1. Patients with plasmacytic leukemia or Waldenstrom's macroglobulinemia or POEMS syndrome (polyneuropathy, organ enlargement, endocrinopathy, monoclonal protein and skin lesions) or amyloidosis at screening;
• 2. Received any prior CAR-T therapy or BCMA targeted therapy;
• 3. Patients who have received autologous hematopoietic stem cell transplantation (ASCT) within 12 weeks prior to monocyte collection or history of allogeneic stem cell transplantation;
• 4. A history of immunodeficiency, including a positive HIV antibody test;
• 5. Hepatitis B surface antigen (HBsAg) positive and HBV-DNA above the lower limit of measurement or 1000 copies /mL (500 IU/mL), (whichever is lower), HCV antibody positive and HCV-RNA above the lower limit of measurement or 1000 copies /mL (whichever is lower);
• 6. Patients who, in the judgment of the investigator, need but are unable to receive prophylactic treatment for Pneumocystis, Herpes Simplex Virus (HSV), or Herpes Zoster (VZV) prior to initiation of treatment, or Syphilis confirmatory positive;
• 7. History of Bacillus Tuberculosis (TB) treatment within 2 years prior to first medication;
• 8. Patients with a history of interstitial lung disease and/or severe lung function impairment;
• 9. Have an active bacterial, fungal, or viral infection;
• 10.A history of severe cardiovascular disease.