A series of P(VDF-TrFE-CTFE)s were synthesized via a well-controlled chemical route including VDF/CTFE copolymerization and dechlorination of P(VDF-CTFE)s to convert CTFE units into TrFE units. The microstructure and properties of the terpolymers were characterized and tested with differential scanning calorimeter (DSC), NMR, dielectric constant and electric displacement-electric field (D-E) hysteresis loop. Thanks to the clean reaction system and ambient reaction condition of VDF/CTFE copolymerization and the hydrogenation of P(VDF-CTFE)s, the terpolymers obtained with high purity and uniformity exhibit a high electric breakdown field of over 500 MV/m, as a result, the highest energy density is obtained as 10.3 J/cm(3). Via comparing the structure and properties of terpolymers; with different compositions and from different preparing processes side-by-side, the TrFE content and the method of TrFE introduced are found to strongly affect the microstructure of the materials and consequently the dielectric properties. The advantages including the lower cost of materials, convenience of the materials preparation and relatively lower energy loss make it possible to be employed as capacitor material. (C) 2008 Elsevier Ltd. All rights reserved.