• Subjects voluntarily participate in this study, sign the informed consent form, and have good compliance;

• Age ≥18 years old;

• Unresectable colorectal adenocarcinoma confirmed by histopathology or cytology;

• After receiving 12 weeks of standard chemotherapy (FOLFOX, FOLFIRI, or CAPEOX) combined with bevacizumab second-line induction therapy, the patients are confirmed as CR, PR, or SD according to RECIST 1.1 criteria;

• The interval between the last second-line induction therapy and randomization is not more than 6 weeks;

• At least one measurable lesion according to RECIST 1.1 criteria;

• ECOG Performance Status 0-2;

• Estimated life expectancy ≥12 weeks;

• Adequate major organ function (no medication for blood component, cell growth factor correction therapy is allowed within 14 days before randomization);

⁃ Women of child-bearing potential must agree to abstain from sex (heterosexual intercourse) or use a reliable, effective method of contraception from the time they provide informed consent until at least 90 days after the last dose of study drug is administered. Serum or urine HCG test must be negative. And must be non-lactating;

⁃ Male participants whose partner is a woman of child-bearing potential must agree to abstain from sex or use a reliable,effective method of contraception from the time they sign an informed consent form until at least 90 days after the last dose of study drug is administered. Male subjects also have to agree not to donate sperm during the same period.