• Able to understand and voluntarily sign a written informed consent form, which must be signed before the designated research procedures required for the study are carried out.

• Age at the time of signing the Informed Consent Form (ICF) is ≥ 18 years old and ≤ 75 years old, both male and female.

• The Eastern Cancer Collaborative Organization (ECOG) has a physical fitness score of 0 or 1.

• The expected survival period is ≥ 3 months.

• Recurrent or incurable metastatic colorectal adenocarcinoma confirmed by Histopathology.(UICC/AJCC colorectal TNM stage System (8th edition 2017))

• Genetic testing revealed RAS (including KRAS and NRAS) mutations, or primary sites located in the right half of the colon (including cecum, rising Colon and proximal 2/3 transverse colon).

• Did not receive systemic treatment for recurrent or metastatic disease.

• According to the RECIST v1.1 standard, there is at least one measurable tumor lesion. Agree to provide archived or freshly obtained tumor tissue samples (formalin fixed paraffin embedded \[FFPE\] tissue wax blocks or at least 5 unstained tumor tissue slice samples) to confirm PD-L1 expression.

• The time interval between the end of adjuvant therapy was \>12 months.

⁃ Having good organ function:

∙ Blood routine examination (no blood components or cell growth factors were used to support treatment within the first 7 days of randomization):

⁃ Absolute neutrophil count (ANC) ≥ 1.5 × 10\^9/L;

• Platelet count ≥ 100 × 10\^9/L;

• Hemoglobin ≥ 9.0g/dL.

‣ Kidney:

∙ Creatinine\<1.5 × ULN, or creatinine clearance rate \* (CrCl) calculated value ≥ 50mL/min;

∙ \*The Cockcroft Fault formula will be used to calculate CrCl: CrCL (mL/min)={(140 age) × Body weight (kg) × F} /(SCr (mg/dL) × 72) Among them: F=1 for males and F=0.85 for females; SCr=serum creatinine. Urinary protein\<2+or 24-hour urine protein quantification\<1.0g.

‣ Liver:

∙ Serum total bilirubin (TBiL) ≤ 1.5 × ULN; AST and ALT ≤ 2.5 × ULN (AST and ALT ≤ 5 for subjects with liver metastasis) × ULN, but not accompanied by elevated bilirubin);

‣ Coagulation function:

∙ International standardized ratio (INR) and activated partial thromboplastin time (APTT) ≤ 1.5 × ULN

‣ Thyroid function: thyroid stimulating hormone (TSH) ≤ ULN; If abnormal, T3 and T4 levels should be investigated, and normal levels Can be selected

⁃ Female subjects with fertility must undergo a serum pregnancy test within 72 hours before the first medication, and the result should be negative. If a female subject with fertility engages in sexual activity with an unsterilized male partner, the subject must adopt an acceptable contraceptive method starting from screening and must agree to continue using the contraceptive method for 120 days after the last dose of the study drug; Periodic abstinence and safe period contraception are unacceptable contraceptive methods. Whether to stop contraception after this time point should be discussed with researchers.

∙ Women with fertility refer to those who have not undergone surgical sterilization (i.e. bilateral fallopian tube ligation, bilateral oophorectomy, or total hysterectomy) or those who have not undergone menopause (defined as those who have ceased menstruation for at least 12 consecutive months without alternative medical reasons, and whose serum follicle stimulating hormone levels are within the laboratory reference range of postmenopausal women);

‣ An efficient contraceptive method refers to a contraceptive method with a low failure rate (such as less than 1% per year) under continuous and correct use. Not all contraceptive methods are efficient. In addition to barrier contraception, female subjects with fertility can also use hormonal contraception (such as birth control pills), intrauterine device contraception, etc. to ensure that pregnancy does not occur.