The purpose of this study is to evaluate the safety and efficacy of cytokine-induced killer cell (CIK) plus S-1 and Bevacizumab vs S-1 and Bevacizumab as Maintenance Treatment for patients with advanced colorectal cancer.

1200 patients with stage Ⅳ colorectal cancer,who had received surgery and chemotherapy,will be randomly divided into group A（receive CIK plus S-1 and Bevacizumab ) or group B（just receive S-1 and Bevacizumab),and the randomize ratio will be 1:1. Patients in group A will receive 3 cycles of CIK treatment (every 1 year) and Apatinib (continuous).Patients in group B will receive only S-1 and Bevacizumab (continuous) .

Inclusion Criteria:

• Patients who can accept curative operations 18-70 years old
• Histologically confirmed with colorectal cancer at stage Ⅳ
• Patients who can accept oral drugs;
• Eastern Cooperative Oncology Group (ECOG) performance status was 0 - 1.

Exclusion Criteria:

• Hemoglobin<8.0 g/dL,White blood cell <3 X 10^9/L;Platelet count <75 X 10^9/L; alanine aminotransferase, glutamic-oxalacetic transaminase, blood urine nitrogen and creatinine more than normal limits on 3.0 times
• Known or suspected allergy to the investigational agent or any agent given in association with this trial
• Pregnant or lactating patients
• Known history of Human Immunodeficiency Virus (HIV), Hepatitis C Virus (HCV) or TreponemaPallidun (TP) infection
• Patients who are suffering from serious autoimmune disease
• Patients who had used long time or are using immunosuppressant
• Patients who had active infection
• Patients who are suffering from serious organ dysfunction
• Patients who are suffering from other cancer
• Other situations that the researchers considered unsuitable for this study.