• Age ≥ 18 years；

• Diagnosis of multiple myeloma (MM) confirmed according to the IMWG diagnostic criteria, with BCMA expression on MM cells determined by flow cytometry or pathology immunohistochemistry;

• Previously treated with at least 2 lines of anti-MM therapy, with at least 1 complete treatment cycle for each line, and evidence of disease progression within 12 months after the most recent anti-myeloma treatment, or being refractory to both immunomodulatory drugs and proteasome inhibitors, with disease progression within 2 months after the most recent anti-myeloma treatment (according to the IMWG diagnostic criteria);

• Disease must be measurable at screening, meeting at least one of the following criteria:Serum M-protein level ≥ 0.5 g/dL; Urinary M-protein level ≥ 200 mg/24h; Serum involved free light chain ≥ 10 mg/dL and an abnormal serum free light chain κ/λ ratio; clinical relapse: a. New bone lesions or soft tissue plasmacytomas (excluding osteoporotic fractures); b. Confirmed increase (≥ 50% increase in SPD of measurable lesions with an absolute value of ≥ 1 cm) in pre-existing plasmacytomas or bone lesions.

• ECOG score 0-2, with an expected survival time ≥ 3 months;

• Bone marrow function at screening (or within 2 months prior to screening) meets the following criteria: a.Hemoglobin ≥ 6 g/dL (no red blood cell transfusion within 1 week before screening), recombinant human erythropoietin is allowed; for patients who meet the ≥6 g/dL criterion at screening, red blood cell transfusion is allowed to maintain hemoglobin ≥ 6 g/dL; b.Absolute neutrophil count (ANC) ≥ 600/μL (no use of granulocyte colony-stimulating factor (G-CSF) within 1 week or pegylated G-CSF within 2 weeks prior to screening); c. Platelet count ≥ 50,000/μL; d. Lymphocyte count ≥ 500/μL; e. Absolute CD3-positive T cell count ≥ 150/μL;

• Renal function at screening (or within 2 months prior to screening) should be normal, with a creatinine clearance ≥ 45 mL/min;

• Liver function at screening (or within 2 months prior to screening) must meet the following criteria: a. Alanine transaminase (ALT) and aspartate transaminase (AST) ≤ 3.0 × the upper limit of normal (ULN); b. Total bilirubin (TBIL) and alkaline phosphatase (AKP or ALP) ≤ 2.0 × ULN (except for congenital hyperbilirubinemia, such as Gilbert's syndrome, where direct bilirubin can be ≤ 1.5 × ULN); c. Albumin ≥ 3 g/dL;

• Cardiac function at screening (or within 2 months prior to screening) must meet the following criteria: a. Left ventricular ejection fraction ≥ 40% (measured by echocardiogram or MUGA scan); b. No clinically significant pericardial effusion detected; c. No clinically significant ECG abnormalities detected;

⁃ Pulmonary function at screening (or within 2 months prior to screening) must meet the following criteria: Oxygen saturation ≥ 90%;No clinically significant pleural effusion detected;

⁃ For women of childbearing potential, a negative pregnancy test must be obtained at screening and prior to drug infusion, and they must not be breastfeeding;

⁃ Male and female subjects of childbearing potential must agree to use effective contraception from the time of informed consent until 1 year after the study drug administration;

⁃ Male and female subjects of childbearing potential must agree not to donate sperm or eggs (oocytes) or other reproductive cells from the time of informed consent until 1 year after the study drug administration;

⁃ The participant or their legally authorized representative must provide written informed consent (ICF), indicating their understanding of the purpose and procedures of the study and their willingness to participate.