Highly conductive polyaniline/sulfonated polystyrene (PANI/HSPS) composites were synthesized by in situ polymerization of aniline within HSPS matrixes. The amount of polyaniline, the conductivity and the morphology of the composite films depend on the sulfonation level of HSPS and the immersion time in the aniline solution. A maximum conductivity of 0.1 S/cm and high transmittance of 80% (at 460–680 nm) have been achieved.