Study to Evaluate the Safety, Tolerance, Pharmacokinetics and Preliminary Efficacy of IBI346#CIBI346Y001#

Inclusion Criteria: 1. According to the multiple myeloma diagnostic criteria of the International Myeloma Working Group (IMWG), there is the initial diagnosis of multiple myeloma. 2. Subjects must have previously received at least 3 anti-myeloma regimens. Subjects must have documented disease progression (according to IMWG criteria) during or within 12 months of completing their last anti-myeloma regimen prior to study entry; and prior regimens must have included proteasome inhibitor (PI) and immunomodulatory drug (IMiD). 3. Measurable disease as defined by the protocol 4. ECOG score is 0 or 1. 5. Expected survival time ≥12 weeks. Exclusion Criteria: 1. Patients suffering from graft-versus-host disease (GVHD) or requiring immunosuppressants drugs. 2. Patients who received autologous hematopoietic stem cell transplantation (ASCT) or prior allogeneic hematopoietic stem cell transplantation (ALLo-HSCT) within 12 weeks prior to mononuclear cell collection. 3. No unmobilized mononuclear cells can be collected for CAR T cell production. 4. Screening subjects who were receiving systemic steroids during the previous 7 days or who were determined by the investigator to require long-term systemic steroid use during treatment (except for inhaled or topical use, except at doses \< 10mg/ day). 5. Patients with a history of hypertension that cannot be controlled by medication (blood pressure ≥140/90 mmHg).