A series of high dielectric constant polymers have been developed with K from 10 to over 50. The high-K polymers have high dielectric breakdown strength above 700 V/μ m and high energy density up to 27 J/cc in labscale small sample test. The capacitor film was produced by using melt-extrusion and biaxial orientation process and film thickness from 2 μ m to 10 μ m has been achieved. Metallized prototype capacitors show promising performance with energy density above 3 J/cc. Future development will target at 10 J/cc energy density in the packaged capacitors. Potential applications include pulsed power capacitors for medical defibrillators, high-power X-Ray/laser system, and direct energy weapon systems.