Abstract: In recent years, with the aggravation of energy crisis, thermoelectric materials which can directly convert heat energy to electric energy have attracted much attention. Among many types of thermoelectric materials, organic-inorganic hybrid nanocomposites have unique advantages. Compared with inorganic materials, organic materials have the advantages of low cost, light weight, good mechanical flexibility and low thermal conductivity. Once different types of addictions are introduced to form nanocomposites, additional phonon-interface scattering can further reduce the thermal conductivity. Moreover, carrier filtering effect induced by band mismatch between organic and inorganic materials enhances Seebeck coefficient. Therefore, abundance works have proved that organic-inorganic hybrid nanocomposites have the potential to obtain promoted thermoelectric figure of merit (ZT), and have bright application prospects in micro-thermoelectric refrigeration devices, flexible wearable power generation devices, temperature sensors and other fields. This paper focuses on the thermoelectric properties of poly(3, 4-ethylenedioxythiophene)∶poly(styrene sulfonate) (PEDOT∶PSS) thermoelectric materials and its nanocomposites. The physical methods and chemical reagent modification methods to improve the thermoelectric properties of PEDOT∶PSS are reviewed. The research progress of the thermoelectric properties of PEDOT∶PSS based nanocomposites with different types of inorganic fillers is further discussed. The inherent mechanisms of the improvement of thermoelectric properties of PEDOT∶PSS based nanocomposites are also revealed in detail.