Exosomes are vesicles secreted by cells, typically ranging from 30 to 150 nm in diameter, and serve as crucial mediators of intercellular communication. Exosomes are capable of loading various therapeutic substances, such as small molecule compounds, proteins, and oligonucleotides, thereby making them an ideal vehicle for drug delivery. The distinctive biocompatibility, high stability, and targeting properties of exosomes render them highly valuable for future treatments of diseases like cancer and cardiovascular diseases. Despite the potential advantage of exosomes in delivering biologically active molecules, the techniques for the preparation, purification, preservation, and other aspects of stem cell exosomes are not yet mature enough. In this paper, we briefly introduce the composition, biogenesis, and benefits of exosomes, and primarily focus on summarizing the isolation and purification methods of exosomes, the preparation of engineered exosomes, and their clinical applications, to better provide new ideas for the development of exosome drug delivery systems.