An effective strategy combining dual-solvent treatment and composite has been proposed to improve the thermoelectric property of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS). Firstly, a composite method with two-dimensional (2D) boron nitride nanosheets (BNNSs), also known as white graphene, was first proposed to improve the Seebeck coefficient of PEDOT:PSS thin film based on an energy filtering effect at the conjunctions. BNNSs were obtained by a facile liquid exfoliation method. Further, a dual-solvent treatment incorporating N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) was performed to optimize the electrical conductivity of PEDOT:PSS/BNNSs hybrid thin films. On the one hand, DMF as first treatment can effectively remove part of the redundant non-conductive PSS leading to an increased electrical conductivity. On the other hand, DMSO as second treatment induced a transformation of PEDOT from benzoid to quinoid structure, resulting in a further enhanced electrical conductivity without a reduction in Seebeck coefficient for PEDOT:PSS/BNNSs. Eventually, a remarkable improvement in thermoelectric power factor was achieved to be 100.1 mu W m(-1) K-2 and a large figure of merit (ZT) was estimated to be 0.12 for PEDOT:PSS/BNNSs(5) hybrid thin film at room temperature.