Suspension of conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) was prepared by chemical oxidation synthesis in water system using 3,4-ethylenedioxythiophene (EDOT) as monomer. Poly(sodium-p-styrenesulfonate) (PSS-Na) was used as dispersant and doping agent. PEDOT:PSS free-standing flexible conductive film was prepared by vacuum filtration. The structure of the polymerized product was characterized by FTIR and UV-Vis. The conductivity, morphology and mechanical properties of PEDOT:PSS film were characterized by four-probe resistance test, SEM and tensile strength test, respectively. The results showed that PEDOT:PSS was successfully polymerized and the optimal conductivity (19.19 S/cm) was achieved when the mole ratio of oxidant to monomer was 0.875. The thickness of free-standing film is approximately 18 μm. The tensile strength of free-standing film reached 45 to 60 MPa at 25 °C and 40% to 60% relative humidity. This indicates that the prepared PEDOT:PSS free-standing film possessed both good conductivity and mechanical properties.