Telomere is located at the end of chromosome and is closely related to chromosome stability in eukaryotic cell. The length of telomeres gradually decreases along with chromosome replication. Cell with over shortened telomeres ultimately end up with death.Telomerase is composed of RNA and protein and maintains telomere length. Compromised telomerase activity leads to decrease of telomere. Therefore, The activation of telomerase and length maintaining of telomereis were necessary for human tumor cells. Mutual regulation of aging and cancer is important since aging caused by telomere induced cell death, which may be a natural barrier for cancer. The authorsperform a systemic review on telomere and telomerase. We try to elucidate the relationship between aging and telomere and regulatory mechanism of telomerase in tumor development, eventually provide guidelines for disease treating.