Objective: To study the relationship between metastatic lymph nodes ratio (MLR) with stage Ⅲ colorectal cancer and its clinicopathological features as well as prognosis. Methods: According to the median number of MLR, 247 patients with stage Ⅲ colorectal cancer were divided into three groups that were low-ratio (≤0.21), middle-ratio (>0.21-0.42) and high-ratio (>0.42) group, respectively. The differences of clinicopathological factors and the 5-year overall survival rate among the groups were analyzed, and the related prognostic factors of the stage Ⅲ colorectal cancer were analyzed by using Cox proportional hazards model. Results: The MLR of 247 cases ranged between 0.02-1.00 with median of 0.21. Of the low-ratio group, the proportion of the well to moderately differentiated colorectal carcinoma was 57.9% (113/195), which was significantly higher than that of the poorly differentiated colorectal carcinoma (23.1%, 12/52) (P＜0.01), and the proportion of the patients who had at least 12 lymph nodes examined was 56.5% (95/168), which was significantly higher than that of the patients who had less than 12 lymph nodes examined (38.0%, 30/79) (P＜0.05). The 5-year survival rate of the low-ratio, middle-ratio and high-ratio group was 67.4%, 28.8% and 6.3%, respectively, and there was a significant difference in 5-year survival rate among the three groups (P＜0.05). The multivariate Cox regression model revealed that the MLR was an important factor for prognosis of stage Ⅲ colorectal cancer. Conclusions: MLR is an important parameter for determining the prognosis of stage Ⅲ colorectal cancer.