Abstract: Using dynamic mesh technology of numeral simulation method, the pressure wave transportation process, created when high-speed train passing through tunnel with ceiling opengings hood on bamboo-truncating portal, was simulated in three dimensions. The calculation result shows that hood with ceiling openings on bamboo-truncating portal does little favor for reducing peak-pressure,but has good effect on reducing peak-pressure gradient. And result also shows that the effect of tunnel hood reducing peak-pressure gradient relevant to the speed of train. On the determining speed, there is optimum aperture ratio.