In this letter, wide temperature dielectric properties and corona resistance of Upilex-S® polyimide (PI) films filled with Zirconium dioxide (ZrO2) nanoparticles were investigated. ZrO2/PI nanodielectrics exhibited the stable dielectric properties, high energy density and high charge-discharge efficiency below 300 °C. Testing of corona resistance showed even a small amount of nanofillers can improve the lifetime of PI significantly. Scanning electron microscopy with x-ray microanalysis (SEM-EDS) analysis suggested the higher thermal conductivity and evaporation of ZrO2 nanoparticles may induce this improvement. These high performance features make polyimide nanocomposites attractive for high energy density capacitor applications at high temperature.