A Clinical Study on the Treatment of Metastatic Colorectal Cancer at the Second-line or Beyond.

Inclusion Criteria:

* Patients pathologically diagnosed with colorectal cancer;
* Received systemic treatment on the first line;
* Age: 18 to 75 years old, gender not limited.
* There must be at least one measurable lesion as the target lesion (in accordance with the RECIST v1.1 standard);
* ECOG: 0-1;
* Expected survival period ≥3 months;
* Women of childbearing age must undergo a blood pregnancy test within 3 days before randomization, and the result must be negative. They must also be willing to take appropriate contraceptive measures during the trial and for 6 months after the end of treatment. For men, it should be agreed to use appropriate methods of contraception during the study period and within 3 months after the end of treatment;
* The subjects voluntarily joined this study and signed the informed consent form.

Exclusion Criteria:

* Patients with wild-type RAS and BRAF, whose primary lesion is located in the left colorectal tract, but who have not received cetuximab as the first-line treatment
* Patients with advanced colorectal cancer who have MSI-H or dMMR
* Those with a history of other malignant diseases in the last five years, except for cured skin cancer and cervical carcinoma in situ
* For patients with a history of uncontrolled epilepsy, central nervous system diseases or mental disorders, the researcher will determine that the clinical severity may prevent them from signing the informed consent form or affect their compliance with oral medication
* Clinically severe (i.e., active) heart disease, such as symptomatic coronary heart disease, New York Heart Association (NYHA) grade II or more severe congestive heart failure, or severe arrhythmia requiring drug intervention (see Appendix 12), or a history of myocardial infarction within the last 12 months
* Those who need immunosuppressive therapy for organ transplantation
* Severe uncontrolled recurrent infections, or other severe uncontrolled concomitant diseases
* The baseline blood routine and biochemical indicators of the subjects did not meet the following criteria: hemoglobin ≥90g/L; The absolute neutrophil count (ANC) is ≥1.5×109/L; Platelet count ≥100×109/L; ALT and AST≤2.5 times the normal upper limit value; ALP≤2.5 times the normal upper limit value; Serum total bilirubin \<1.5 times the normal upper limit value; Serum creatinine \<1 times the upper limit of normal; Serum albumin ≥30g/L
* Those known to have a deficiency of dihydropyrimidine dehydrogenase (DPD)
* Those who are allergic to any investigational drug ingredients (such as irinotecan, irinotecan liposome, capecitabine, bevacizumab and camrelizumab)
* Pregnant or breastfeeding women
* Have received any of the following treatments:

The concomitant medication contained CYP3A4, CYP2C8 strong suppressor/strong inducer or UGT1A1 strong suppressor within 2 weeks prior to randomization;Use immunosuppressants or systemic hormones for immunosuppressive purposes within 2 weeks before randomization (dose \>10mg/ day, prednisone or other equivalent therapeutic hormones); \<s:1\> Received radiotherapy within 2 weeks prior to randomization;Undergo major surgeries (such as thoracotomy, laparotomy, etc.) within 4 weeks before randomization;The patient has received any other clinical study drug treatment within 4 weeks prior to randomization, unless it is an observational (non-interventional) clinical study or follow-up of an interventional clinical study.

\- Abnormal coagulation function, with a bleeding tendency, or currently undergoing thrombolytic or anticoagulant therapy. Prophylactic use of low-dose aspirin (≤100mg/ day) and low-molecular-weight heparin (enoxaparin 40mg/ day and other low-molecular-weight heparin at equivalent doses) is permitted.