PIWI -interacting RNAs（piRNA）are novel small -molecule non -coding RNAs that mediated by interacting with PIWI proteins. They are mainly among Droflies，mammalian（human，mouse，etc.）stem cells and germ cells. More and more studies have shown that piRNA can regulate gene expression through epigenetic changes，including transposon silencing，DNA methylation and chromatin modification，and play a key role in the occurrence of tumors. Therefore，piRNA has the potential as a biomarker to provide a new method for cancer diagnosis and prognosis monitoring. This article reviews the biological role of piRNA in colorectal cancer， providing clues for the pathogenesis of colorectal cancer and the search for its effective biomarkers.