Whether chemotherapy is needed after surgery for colorectal cancer mainly depends on the postoperative staging. The post-operative chemotherapy is not required for stage IIA or above, but can be observed closely; below stage IIA, chemotherapy is generally required. Stage IIA may not be treated with chemotherapy, but the following high-risk factors are considered: poor differentiation of tumor (pathology grade 3-4), preoperative intestinal obstruction or local perforation, proximity of incisional margin to tumor, undetermined nature of incisional margin or positive incisional margin, lymphatic and/or vascular infiltration, incomplete surgical lymph node dissection (at least 12 lymph nodes are required for colorectal cancer surgery), etc. It should be reminded that postoperative adjuvant chemotherapy for stage II colorectal cancer can improve the survival rate by no more than 5%.