Electroactive polymers (EAPs) are novel polymeric materials that generate large displacement or strain under electrical field. EAPs show many attractive features such as high electromechanical response, environmental tolerance, lightweight, flexibility, biocompatibility and long-term durability. In 1998, we reported the discovery of a new class of EAP, e.g., high energy electron irradiated P(VDF-TrFE) (poly(vinylidenefluoride-trifluoroethylene)) based electrostrictive polymers, showing large electrostrictive strain (-5%) and relaxor ferroelectric characteristic. Since then, the P(VDF-TrFE) based terpolymers were developed which eliminate the irradiation process. P(VDFTrFE-CFE) terpolymer exhibits very high electromechanical responses (elastic energy density ∼ 1.1 J/cm and electromechanical coupling factor ∼55%). Further, blends approach was studied to increase elastic modulus. Devices based on the high electrostrictive polymers have also been demonstrated, such as micro pump, braille displays, soft robot, et al. These results suggest that P(VDF-TrFE) based electrostrictive polymers are promising for many electromechanical device applications.