The invention discloses a miRNA marker associated with colorectal cancer metastasis in plasma and an application thereof and belongs to the technical fields of biotechnologies and medicine. The miRNAmarker associated with colorectal cancer metastasis in plasma is one or more of miR-96, miR-99b, miR-155, let-7a and let-7b. The specificity and sensitivity of the miRNA marker associated with colorectal cancer metastasis in plasma screened in the invention for predicting the colorectal cancer metastasis are obviously higher than those of a clinically used tumor marker CEA at present, and the diagnostic accuracy is greatly improved.