Abstract: Bipolar junction transistors may be burned out by injected electromagnetic pulse. The circuits play important rolls because EMP is always coupled to circuit by antenna or aperture firstly and injected in BJT by circuit afterwards. The current distribution coefficient was studied, on the basis of which the influences of three kinds of typical components were studied with our 2-dimentional mixed-level circuit and device simulator. The conclusion is that a resistor at base has little influence on burnout process, a positive voltage source at collector has the effect of lowering the amplitude of EMP by the voltage of the source and a resistor at collector can significantly improve the durability of device against EMP.