In　the　paper　the　breakdown　characteristics　of　Printed　Circuit　Board　(PCB)　paralleled　traces　is　investigated.　Rectangular　pulse　with　single　pulse　mode　and　repetition　frequency　pulse　mode　is　injected　directly　to　paralleled　traces　structure　on　PCB.　To　obtain　desired　pulse　waveforms,　a　pulsed　power　generator　is　designed　and　set　up　which　can　output　rectangular　pulses　with　different　pulse　widths,　pulse　repetition　frequency　(PRF)　and　amplitudes.　Experimental　results　show　that　the　breakdown　behavior　between　paralleled　traces　can　be　considered　as　＇solid-gas＇　composite　dielectric　breakdown,　and　the　breakdown　characteristics　are　related　to　spacing　of　paralleled　traces,　pulse　width,　PRF　and　pulse　duration,　etc.　Generally　the　breakdown　voltage　(Ubd)　rises　as　trace　spacing　or　pulse　width　increases　and　decreases　as　PRF　or　pulse　duration　increases.　Overall,　the　research　of　susceptibility　of　PCB　trace　with　conducted　pulse　injection　could　provide　certain　suggestions　for　PCB　EMC　design.　©　2011　The　Institute　of　Electrical　Engineers,　Japan.