Abstract: MicroRNA-31 (MiR-31) is a multifunctional miRNA widely found in animal and human tissues, which can regulate the expression of target genes and participate in physiological and pathological processes such as cell proliferation, differentiation and apoptosis. The miR-31 is closely related to the occurrence and development of tumors. The miR-31 can be expressed in various tumors as a tumor suppressor or tumor promotion gene, and plays an important role in multiple biological processes such as tumor cell proliferation, invasion and migration. Therefore, miR-31 is expected to be a novel biomarker and therapeutic target for malignant tumors. This article reviewed the research progress in the mechanism of action and treatment prognosis of miR-31 in malignant tumors in order to provide strategies for early diagnosis and personalized treatment of malignant tumors.