The experiment of damage effect on Si bipolar transistor-low noise amplifier injected the microwave pulse in experimental platform. In the failure analysis of Si bipolar transistor-low noise amplifier with microwave pulse, the transistor was permanently damaged when the gain of lownoise amplifier decreased more than 10 dB. The electrical characteristic of the Si bipolar transistor was measured before and after its damage and the micro-characteristic of the damaged transistor was observed by scanning electron microscope. Results show that when the Si bipolar transistor is damaged with microwave pulse, the ablative Si material in the base region causes short circuit of emitter junction and collector junction, which have the consequences of losing the PN junction characteristics and leading to failure devices.