Abstract: Polyaniline (PANI) was prepared in the presence of methanesulfonic acid (MSA) as the dopant. Then PANI pyridine based polybenzobisoxazole (PANI-PBOPy) composites with different PANI contents were prepared by using MSA as solvent. The structure and morphology of composites were fully characterized by FT-IR, WXRD, UV Vis, TGA and SEM. The effect of mass fractions of PANI, tempe rature and frequency on the electrical property and dielectric property were studied. Results suggested that the electrical conductivity of composites was increased by 10 orders of magnitude when mass fraction of PANI was 20% in the composites. The dielectric constant and dielectric loss of composites firstly increased and then decreased when PANI content increased. They had a sharp drop at low frequency and tended towards stability at high frequency. However, they increased with the increasing of temperature. When the temperature was 40 °C and the mass fraction of PANI was 15%, the dielectric constant of composite was about 230.