Abstract: The quantity of plantation waste in China is huge, its resource utilization is of great significance, and the conversion of plantation waste into biochar is an important way to realize efficient utilization. Biochar is a solid product obtained by thermal conversion of biomass raw materials in an oxygen-free or oxygen-limited environment, which has a wide range of applications in many fields due to its high carbon content, high cation exchange capacity, large specific surface area and stable structure. In this paper, the preparation and modification of biochar as well as the application of biochar-based composites in different fields are systematically summarized and generalized. Furthermore, the important application value of biochar-based composites prepared from biochar in the fields of adsorption, catalysis, slow-release fertilizers, energy storage, sensing, and electromagnetic interference (EMI) shielding are introduced.