In this paper, highly conductive poly(3,4-ethylenedioxythiphene):poly(styrenesulfonate) (PEDOT:PSS) thin films realized by incorporating secondary doping technique with post-treatment process is demonstrated. The conductivity of the PEDOT:PSS film enhanced greatly from 0.6S/cm to 736S/cm after 1.25% of p-toluenesulfonic acid solution was doped into the PEDOT:PSS dispersion. The post-treatment using dimethyl sulfoxide further improved the conductivity to 1549S/cm. We found that the electro-optical properties of the polymer dispersed liquid crystal (PDLC) cells fabricated by the highly conductive PEDOT:PSS films were comparable to those constructed by ITO. This work reveals that highly conductive PEDOT:PSS film is a suitable material for manufacturing ITO-free liquid crystal devices.