Approximately half of colorectal cancer (CRC) patients were first diagnosed after 70 years old. However, compared with younger patients, elderly patients were often undertreated in chemotherapy due to their impaired tolerance. Recently, there have been great controversy on adjuvant chemotherapy strategy for stage II/III CRC patients. As an oral fluoropyrimidine, capecitabine has been demonstrated to be equivalent to i.v. 5-Fu/leucovorin regimen in stage III CRC patients. In light of fewer adverse effects and better flexibility, capecitabine was regarded as an ideal alternative for elderly CRC patients, but the optimal dosage for stage II/III elderly CRC patients still remains inconclusive. Our trial expected to prospectively randomized 710 postoperative stage II/III elderly CRC patients (between 70 and 90 years of age) to adjuvant mono-chemotherapy with a standard dose of capecitabine (2500 mg/m2/day) or a reduced dose (2000 mg/m2/day). This is a non-inferiority phase 3 trial with a primary endpoint of 3-year disease free survival (DFS), and other outcomes include 3-year overall survival(OS), completion rate, toxic and adverse effects and quality of life(Qol). By this trial, we aimed to achieve more precise evidence on the individualized adjuvant chemotherapy strategy for stage II/III elderly CRC patients.