In this paper, charge storage stability of constant voltage corona charged Mylar PETP at room and elevated temperature is discussed. Significant difference between influence of dipole peak at low temperature for Mylar PETP and that of real charge peak at lower temperature for nonpolarity fluoropolymers on charge stability is analyzed. The influence of bulk conduetivity of Mylar PETP charged at RT and elevated temperature on mean charge depth and the charge transport model in the bulk during TSI) after charging at RT for Mylar PETP are studied by means of conductivity glow curve measurement and heat pulse technique.