High-performance dielectric nanomaterials have received increasing attention due to their important applications in the field of energy storage. Among various dielectric materials, polymer nanocomposite is one of the most promising candidates. However, the problems of environmental pollution caused by polymer-based dielectric materials have been extensively studied in recent years, which need to be solved urgently, leading to the search for new biodegradable dielectric materials. Herein, we report composite materials based on biodegradable and renewable chitin and molybdenum disulfide (MoS2) nanosheets for the first time. The MoS2 nanosheets were first fabricated by glycerol/urea system and then KOH/urea aqueous solution was used to directly dissolve chitin at low temperature together with the dispersion of the MoS2 nanosheets in a simple green process. The two-dimensional MoS2 nanosheets possess high polarization strength, and a large specific surface area can enhance the interfacial polarization with chitin; meanwhile, it can serve as a charge breakdown barrier to hinder the propagation of electrical tree branches. The results also show that the dielectric constant and breakdown strength of the chitin/MoS2 nanocomposites were increased, while the dielectric loss remained low. When the MoS2 content was 5 wt %, the charge and discharge efficiencies of the composite film were more than 80%, and the breakdown strength also reached 350 MV m(-1), thus resulting in a high discharge energy density of 4.91 J cm(-3), which was more than twice of the neat chitin (2.17 J cm(-3)). Furthermore, the nanocomposite films exhibited good thermal stability. Therefore, these chitin-based nanocomposite films are promising as high-performance biomass-based dielectric capacitors.