High gain and high-efficiency Cascode Class-E power amplifier (PA) with Reconfigurable Filter Network for wireless application system using 0.25µm GaN technology is presented in the paper. Cascode Class-E PA is combined with a transmission line and Micro strip inter digital capacitor (MICAP) to illustrate a harmonic balance matching technique. The PA is composed of two stages and adopts a current source inter digital microwave capacitor (CSTIMC) and Cascode Class-E. This technique also enhances the resonant circuits band properties. Micro strip inter digital capacitor (MICAP) helps to enhance an internal matching design. For maximum output power, drain efficiency, and PAE the fundamental and second harmonic impedances are to be accurately improved for the particular operating frequency. The results represent maximum output power of 43.1dBm, drain efficiency of 74.5 % and power added efficiency (PAE) of 67.8 %. The fundamental and second harmonic balance levels are adjusted at -21dBc to -16dBc. The simulated and the measured results of the proposed power amplifier show the right consistency.