In this study,the authors reported an influence of activated carbon fibres(ACFs)with different specific surface areas on the thermal conductive and electrical insulating properties of polymeric composites.Here,the polyamide-imide composites were obtained via solution blending and cured method.The composites exhibited thermal conductivity(TC)up to 0.62 W·m^(−1)·K^(−1).In addition,the composites were still insulating,having an electrical resistance of 0.7 MΩ.The experimental results suggested that the mechanical and electrical insulating properties decreased with the increasing of the specific surface area of the ACFs.Meanwhile,it was found that the introduction of boron nitride was conducive to the TC and electrical insulating properties of the polymeric materials.