Chitosan, a renewable, non-toxic, and natural cationic polyelectrolyte, can be combined with many anionic polyelectrolytes (such as sodium alginate, hyaluronic acid, xylan, and gelatin) via electrostatic forces to form chitosan-based polyelectrolyte composites under certain conditions. This review summarizes various methods of preparing chitosan-based polyelectrolyte composites and analyzes their applications in clinical medicine and agriculture, as well as pharmaceutical, tissue, food, environmental, and textile engineering fields. The future development direction and potential of chitosan-based polyelectrolytes are also discussed.