In- situ oxidative polymerization of poly (3, 4-ethylenedioxythiophene) (PEDOT) is widely used in the preparation of functional composite materials. How to optimize the oxidative polymerization conditions of PEDOT to improve the conductivity of PEDOT materials after in-situ growth has become an important research direction. The conductive polymer PEDOT was synthesized by chemical oxidative polymerization with ferric nitrate nonhydrate(Fe(NO₃) ₃ · 9H₂O) as oxidant. The effects of dopant type, polymerization temperature, monomer concentration and ratio of monomer to oxidant on the chain structure and conductivity of PEDOT were studied. The results show that the conductivity of PEDOT is the highest when the reaction time is 4 h at 60 ℃, the monomer concentration is 7 g/L, and the mole ratio of monomer to oxidant is 1: 1, with water as reaction solvent and ferric nitrate nonhydrate as oxidant.