In order to study the irradiation characteristics of SiGe heterojunction bipolar transistors with different emitter areas at extreme temperatures,characteristics of irradiated power SiGe heterojunction bipolar transistors (SiGe HBTs) were systematically analyzed at different temperatures in this paper; Correlation between emitter area and power SiGe HBTs'' irradiation damage of SiGe HBTs was revealed.Modeling of power SiGe HBTs device was conducted to extract the main internal parameters of the device affected by irradiation. The variation of electron density (Δ edensity), carrier recombination (Δ SRH recombination) and carrier mobility (Δ emobility) before and after irradiation were characterized, whose affecting mechanism on power SiGe HBTs irradiation was systematically analyzed. The results show proportional proton irradiation damage of emifferarea on power SiGe HBTs.SiGe HBTs have better proton irradiation resistance at extreme temperatures.which presents great potential in the field of radiation resistance and space application.