This study aimed to investigate risk factors and prognosis ofcolorectal cancer in patients over 80 years ofage. Surgical risk was evaluated by colorectal POSSUM(CR-POSSUM)and prognosis by Glasgow prognostic score(GPS). The analysis included 56 patients aged over 80 years with colorectal cancer during 2002-2012. Mean operation time, blood loss, and period ofhospitalization were 130 min, 111 mL, and 19.9 days, respectively. Postoperative complications occurred in 26 patients (46.4%; complications group). The 5-year overall survival rate for patients with complication scores above 2 was 51.1%, compared to 82.3% in a control group, and patients in the complication group also exhibited a poorer prognosis. CR-POS SUM scores were significantly higher in the complication group than in the control group in PS, OS, and PMR. Further analysis revealed that patients with GPS 0 or 1 had a significantly higher 5-year survival rate(84.9%)than those with GPS2(38.9%, p <0.05).