Abstract: Abstract：Objectives In this paper, the damage characteristics of Gallium nitride (GaN) based low noise amplifier (LNA) under high power microwave pulses are discussed. Methods High power microwave with different pulse widths and pulse numbers was studied to investigate the changes of DC and RF parameters of GaN LNA. In the experiment, the threshold power of the device was obtained through continuous wave and microwave pulse test with different pulse width and duty cycle. At the same time, in order to further determine the damage area of LNA and the physical mechanism of damage, the surface and internal area of the chip was observed by microscope and dual beam FIB devices after the chip was unpackaged. Results The experimental results show that when the GaN LNA was injected with sufficient power of microwave pulse injection shock with a pulse width of 30 ns, a rising edge of 18 ns, and a falling edge of 18 ns with a period of 2 ms, the gain of the LNA decreases from 23.67dBm to -8.91dB, the noise factor increases from 1.59dB to 18.13dB, and the output waveform of the LNA is compressed strongly. The damage is mainly due to the formation of a micro-current channel at the gate due to a high-power microwave attack, which then causes a drain overcurrent and permanently damages the device.Conclusions The study on damage effect of GaN LNA under high microwave pulse conditions provides important reference value for further understanding the impact of high-power microwave pulses effects on GaN LNA and improving its robustness.