Abstract: Objective To investigate the correlations between the expression of telomerase activation and carcinogenesis and prognosis of colorectal cancers. Methods Immunohistochemistry was used to detect the expressions of telomerase in 48 tissues of colorectal cancer, 19 tissues of colorectal adenoma and 11 tissues of adjacent non-tumorous mucosa and its relations with clinicopathologic factors were analysed. Results The positive expression rate of telomerase in colorectal cancer were 87.5%, which was significantly higher than the rate 26.3%（5/19）in 19 tissues of colorectal adenoma（P＜0.05）,and 0.0%（0/11）in 11 adjacent normal tissues（P＜0.05）.The statistical analysis showed that the expression level of telomerase activation was positively correlated with pathology rank, lymph node metastasis and clinical stage（P＜0.05）. Conclusion There were a positive correlation between the expression of telomerase and carcinogenesis of colorectal cancer. The detection of telomerase may be helpful in evaluation of the prognosis of colorectal cancers.