• Aged 18-75 years, gender is not limited;

• Patients diagnosed as relapsed/refractory multiple myeloma according to the International Myeloma Working Group (IMWG 2014) criteria for multiple myeloma after at least 3 lines of treatment (including at least one proteasome inhibitor and an immunomodulator based chemotherapy regimen), and at least one complete treatment cycle per line of treatment; Documented disease progression during or within 12 months after the most recent antimyeloma therapy (not limited to 12 months after CAR-T therapy as the last line of therapy);

• The presence of one or more measurable lesions at screening was defined as any of the following: 1) serum M-protein ≥0.5g/dL (≥5g/L), 2) urinary M-protein level ≥200 mg/24 hours; 3) serum free light chain (sFLC) ≥100 mg/L and serum κ/λ free light chain ratio abnormal (\<0.26 or \>1.65);

• Good organ function;

• ECOG score ≤1;

• The predicted survival time was ≥12 weeks;

• Female subjects of childbearing age or male subjects with partners of women of childbearing age agreed to use effective methods of contraception throughout the trial and for 12 months after cell infusion;

• The subjects voluntarily participated in the study, signed the informed consent form, and complied with the follow-up.