Biodegradable composite films based on chitosan and lignin with various composition were prepared via the solution-casting technique. FT-IR results indicate the existence of hydrogen bonding between chitosan and lignin, and SEM images show that lignin could be well dispersed in chitosan when the content of lignin is below 20 wt% due to the strong interfacial interaction. As a result of strong interaction and good dispersion, the tensile strength, storage modulus, thermal degradation temperature and glass transition temperature of chitosan have been largely improved by adding lignin. Our work provides a simple and cheap way to prepare fully biodegradable chitosan/lignin composites, which could be used as packaging films or wound dressings.