∙ Subjects must meet all the following criteria to be eligible for the study:

• Age≥18 years, regardless of gender.

• Diagnosed with advanced, metastatic, or recurrent malignant tumors confirmed by histology or pathology, primarily including colorectal cancer, esophageal cancer, gastric cancer, pancreatic cancer, lung cancer, or cholangiocarcinoma.

• Failure of at least second-line standard therapy (due to disease progression or intolerance, such as surgery, chemotherapy, radiotherapy, etc.) or a lack of effective treatment options.

• Immunohistochemical staining of tumor samples within 3 months confirming CEA positivity (distinct membrane staining with a positivity rate of≥10%); if the immunohistochemical result of the tumor sample is more than 3 months old at the time of screening (distinct membrane staining with a positivity rate of≥10%), the patient's serum CEA must exceed 10µg/L.

• At least one evaluable lesion according to RECIST 1.1 criteria.

• ECOG score of 0-2 (Appendix 2).

• No severe psychiatric disorders.

• Unless specifically stated otherwise, subjects' major organ functions must meet the following conditions:

‣ Blood routine: WBC\>2.0×109/L, neutrophils\>0.8×109/L, lymphocytes\>0.5×109/L, platelets\>50×109/L, hemoglobin\>90g/L;

⁃ Cardiac function: Echocardiography indicating a left ventricular ejection fraction≥50%, and no significant abnormalities on electrocardiogram;

⁃ Renal function: Serum creatinine≤2.0×ULN;

⁃ Liver function: ALT and AST ≤3.0×ULN (may be relaxed to≤5.0×ULN if liver tumor infiltration is present);

⁃ Total bilirubin≤2.0×ULN;

⁃ Oxygen saturation\>92% without supplemental oxygen. 9. Eligible for apheresis or venous blood collection, with no contraindications for cell collection.

‣ 10\. Subjects agree to use reliable and effective contraceptive methods from signing the informed consent form until 1 year after receiving CAR-T cell infusion (excluding natural family planning methods).

‣ 11\. The patient or their guardian agree to participate in this clinical trial and signs the ICF, indicating an understanding of the trial's purpose and procedures and willingness to participate.