Abstract: MicroRNA (miRNA) is an important gene regulatory molecule involved in the occurrence of a variety of diseases and is relat-ed to tumors. MicroRNA has become a new direction of oncology research in recent years. Studies showed that miR-29plays dual roles, as tumor suppressor and tumor promoter. The expression of miR 29significantly differs between cancer and normal tissues. miR-29is predicted to be a biomarker for early diagnosis and prognosis prediction of certain cancer. This paper reviews the role of miR- 29 in the pathogenesis of cancer.