Inclusion Criteria:  65 years and older; Histologically or cytologically confirmed unresectable metastatic colorectal cancer refractory to or unfit for standard therapies; ECOG PS 0-1; At least 4 weeks after the last anti-tumor therapy (chemotherapy, radiotherapy, biotherapy or hormone therapy) and more than 3 months after operation treatment before enrollment; Life expectancy ≥ 3 months; Cooperative in observation of adverse events and curative effect; No other anti-tumor concomitant treatment (including steroid drugs); Adequate organ and bone marrow functions; At least one measurable lesion(s); Signed the written informed consent and completed the geriatric questionnaire (G8 screening form) at the time of enrollment.  Exclusion Criteria:  Active upper gastrointestinal ulcer, obvious vomiting, chronic diarrhea, intestinal obstruction, absorption disorder, etc which may affect drug absorption, distribution, metabolism, or clearance; Evidence of central nervous system metastasis; One of the following complications: uncontrolled hypertension, coronary artery disease, arrhythmia and heart failure; Abuse of alcohol or drugs; Less than 4 weeks from the last clinical trial; Previous treatment with VEGFR inhibitors; Severe uncontrolled disability with concurrent infection; Proteinuria ≥ 2 + (1.0g / 24hr); Uncontrollable gastrointestinal bleeding; Arterial / venous thromboembolic events such as cerebrovascular accident (including transient ischemic attack) occurred within 12 months before the first dose; Acute myocardial infarction, acute coronary syndrome or coronary artery bypass grafting occurred within 6 months before the first dose; Fracture or wound that has not been cured for a long time; Coagulation dysfunction, bleeding tendency or receiving anticoagulation treatment; Congenital or acquired immune deficiency (such as HIV infection), or active hepatitis (HBV DNA ≥ 103copies / ml after regular antiviral therapy); Patients who are not suitable for the study judged by the researchers.