Objective To investigate the value of circulating tumor cells (CTC) in evaluating the efficacy of chemotherapy in patients with postoperative stage Ⅲcolorectal cancer (CRC). Methods A total of 77 patients with postoperative stage ⅢCRC treated in Department of Oncology, the First People′s Hospital of Jingdezhen City from January 2017 to January 2019 were selected as the research object. 5 ml of peripheral venous blood was collected from patients on fasting in the morning within 1 week before postoperative adjuvant chemotherapy and after 2 courses of adjuvant chemotherapy, and the expression of various types of CTC in peripheral blood was detected to analyze the relationship between positive total CTC before chemotherapy and clinicopathological features. According to the follow-up, patients were divided into stable disease (SD) group (30 cases) and progressive disease (PD) group (47 cases), and the correlation of CTC count changes before and after chemotherapy and the relationship of total CTC count changes after chemotherapy with disease-free survival (DFS) and overall survival (OS) were analyzed. Results Before chemotherapy,there were no statistically significant differences in the total CTC positive rate of patients with different age, gender,degree of differentiation, location, TN stage and with or without hematochezia (P＞0.05). The changes of total CTC, epithelial CTC, interstitial CTC and mixed CTC before and after chemotherapy were negatively correlated with the efficacy of chemotherapy (r=-0.301, r=-0.334, r=-0.281, r=-0.326, P＜0.05). After chemotherapy, the patients were divided into descending group and ascending group according to the trend of total CTC count. The mean DFS and OS of descending group (22.9 and 24.8 months) were longer than those of ascending group (9.0 and 15.7 months), and the differences were statistically significant (P ＜0.05). Conclusion The changes of various types of CTC count before and after chemotherapy can be used to evaluate the chemotherapy efficacy of postoperative stage ⅢCRC patients to a certain extent, and the changes of total CTC count affect the length of DFS and OS.