Abstract: During the experiments on electromagnetic pulse (EMP) action utility of micro-electronic components, aimed at three kinds of micro-wave low-noise silicon dynatron transistors, positive EMP (including ESD and square-wave EMP) stresses were injected into all the combinations (CB, BC, CE, EC, EB and BE). Through recording and comparing the damaged voltage of each injected combination, it can be found that the most sensitive port to EMP of micro-wave low-noise transistors is not EB (emitter-base) but CB (collector-base). By analyzing the device fabric and the process of discharge, the failure mechanism of CB and EB is separately determined. So it makes clear that CB is more sensitive to EMP than EB.