Abstract: Objective To explore the influence of laparoscopic CO2 pneumoperitoneum on blood metastasis of colorectal cancer.Methods Sixty colorectal cancer patients were randomly divided into laparoscopic surgery group and open surgery group.RT-PCR was used to detect the expressions of CK20mRNA before treatment,in operation and after operation,and effect of different surgical methods on the metastasis of tumor cells in peripheral blood was analyzed.Results There were no significant differences in positive expression of CK20mRNA before treatment,in operation and after operation between two groups (P ＞ 0.05).There was no significant difference in 3-year survival rate between the two groups (P ＞ 0.05).Conclusion Laparoscopic CO2 pneumoperitoneum does not increase the positive rate of CK20mRNA in peripheral blood in treatment of patients with laparoscopic resection of colorectal cancer.