This study is a single-center exploratory clinical trial. It is estimated that 6-12 subjects will be enrolled. The "BOIN" dose escalation design is adopted. The main purpose is to evaluate the safety of FKC288 in the treatment of subjects with relapsed or refractory AL amyloidosis and explore the recommended phase II dose of FKC288 in the treatment of patients with relapsed/refractory systemic Light Chain (AL) amyloidosis.

A leukapheresis procedure will be performed to manufacture FKC288 chimeric antigen receptor (CAR) modified T cells. Bridging therapy is allowed between PBMC collection and lymphodepletion. Lymphodepletion with fludarabine and cyclophosphamide was performed for three consecutive days. After 1-day rest, subjects will receive a single dose infusion of FKC288 at 0.1, 0.3, 1.0, or 3.0x 10^6 CAR+ T cells/Kg. Subjects will be followed in the study for a minimum of 2 years after FKC288 infusion.

Inclusion Criteria:

1. The subject must personally sign a written informed consent form approved by the ethics committee before the start of the study;
2. The subject's age is ≥18 years old and <70 years old;
3. The subject must be diagnosed with light chain amyloidosis by pathological examination, with at least one major organ involved (heart, kidney, or liver);
4. The subject with recurrent/refractory light chain amyloidosis that achieved no response with conventional treatment;
5. dFLC > 50mg/L;
6. Expected survival ≥ 12 weeks;
7. ECOG score ≤ 2 points;
8. Female subjects with fertility should agree to practice an effective method of contraception from the day of signing the ICF until 365 days after the infusion. An effective method of contraception is defined as abstinence or contraceptive methods with an annual failure rate of <1% specified in the plan.
9. Before enrollment, the subject must have appropriate organ function and meet all the following criteria:

1) Absolute neutrophil count ≥ 1.0×109/L (use of granulocyte colony-stimulating factor (G-CSF) support is allowed, but must be without supportive treatment within 7 days before the examination); 2) Platelet count ≥ 75×109/L (no transfusion support [including component transfusion] or treatments aimed at raising platelets such as thrombopoietin [TPO] should be received within 7 days before the examination); 3) Hemoglobin ≥ 9 g/dl (no transfusion support [including component transfusion] should be received within 7 days before the examination); 4) Bilirubin value ≤ 1.5× upper limit of normal (ULN) (except bile duct obstruction caused by tumor compression); 5) Creatinine clearance rate ≥ 40 ml/min; 6) ALT or AST ≤ 2.5× ULN (≤5 times the upper limit of normal in patients with liver involvement); 7) Echocardiography results indicate left ventricular ejection fraction ≥ 50% with no significant pericardial effusion; 8) NTproBNP < 1800pg/ml, TNT < 0.06ng/ml; 9) Stable coagulation function: INR ≤ 1.5, APTT ≤ 1.2× ULN (excluding tumor-related anticoagulant therapy); 10) >95% basic blood oxygen saturation in the natural indoor air environments.

Exclusion Criteria:

1. Subjects who have received any of the following treatments prior to enrollment: 1) Subjects who have received gene therapy before enrollment; 2) Subjects who have received live vaccines within 4 weeks prior to enrollment; 3) Subjects has received other interventional clinical research drugs within 12 weeks before apheresis.
2. Subjects with central metastasis or complete intestinal obstruction.
3. Subject with moderate or more severe hydrothorax and ascites which are hard to control by conventional treatment and require continuous catheter drainage.
4. With an active malignant tumor in the past 5 years, unless it is a curable tumor and has been obviously cured.
5. Subjects who are positive for hepatitis B surface antigen (HBsAg) or hepatitis B core antibody (HBcAb) and have abnormal peripheral blood HBV DNA test results (HBV DNA test abnormality is defined as HBV DNA quantitative detection is higher than the detection center's detection lower limit or higher than the detection center's normal reference range or HBV DNA qualitative detection is positive); hepatitis C virus (HCV) antibody positive and peripheral blood hepatitis C virus (HCV) RNA positive; human immunodeficiency virus (HIV) antibody positive; the cytomegalovirus (CMV) DNA positive; syphilis testing RPR positive.
6. Presence of uncontrollable active infections (excluding \