Objective To explore the values of telomerase in the diagnosis, therapy and prognostic parameter of colorectal cancer. Methods Telomerase activity in colorectal cancer, peri-cancerous and normal mucosa was detected by PCRTRAP-ELISA assay. Results The positive rates of telomerase in colorectal cancer, peri-cancerous and normal mucosa were 84.8%, 20.0% and 0% respectively. 66.7% of the early stage colorectal cancer expressed telomerase. Telomerase activity was reversely correlated with tumor differentiation.Conclusion Telomerase may be an earlier event of malignant progression in colorectal cancer. It might be a parameter for diagnosis of colorectal cancer.