Abstract: Mesenchymal stem cells (MSCs) are a kind of stem cells with high self-renewal ability and multi-directional differentiation potential. They can differentiate into a variety of different cells. Studies have shown that mesenchymal stem cell-derived exosomes (MSC-EXO) are the main components of tumor microenvironment and play an important role in the occurrence and development of malignant tumors. Exosomes are a kind of extracellular vesicles secreted by eukaryotic cells; they can transmit bioactive molecules such as lipids, nucleic acids and proteins between cells, and they widely participate in the exchange of information between cells. This article reviews the role of mesenchymal stem cell-derived exosomes in malignant tumors and their application prospect.