Abstract: Polymer-based dielectric capacitors are widely used in the fields of electric and military industry due to the excellent electrical properties. However, the low energy storage density limits the development. Thus, it is imperative to research and develop polymer materials with high discharge energy density. Two important indicators for evaluating the energy storage characteristics are discharge energy density and energy storage efficiency. In order to increase the discharge energy density and stabilize the energy storage efficiency, many theories and methods are proposed and applied. Based on material properties and preparation methods, the current domestic and foreign research progress on energy storage characteristics composite systems are introduced, mainly focusing on all-organic composite systems and inorganic/organic composite systems. The restrictions on the research are discussed.