Abstract: This paper studies low noise amplifier (LNA) failures under intentional electromagnetic environment (IEME) through SPICE simulation and direct injection experiment. The classic single-stage studied has strong gain suppression effects when superimposed with high-power microwave (HPM) pulse at input port. Both theoretical and experimental results obtained highlight that the SPICE model can be used to assess IEMI effects. The LNA gain-suppression duration will keep the maximum value when the injected microwave pulse width exceeds its threshold for fixed pulse power level. The duration can be well estimated by the RC constant of transistor base bias circuit. Finally, the mechanism of such LNA failure is discussed.