An in-situ simulation explosion test is carried out at a site with Ningbo marine silt soft soil. The history and evolution laws of excess pore water pressure, shock pressure and temperature on the conditions of different explosive quantity and buried depth are obtained. The test results reveal the existence of coupling phenomena of seepage, stress and temperature. It is also shown that the peak of excess pore water pressure increases with the increase of explosive quantity and the dissipation of pore pressure is relatively quick in early minutes after the explosion and then it decreases. A dividing pressure which means a value from shock wave to elastic wave is determined and it found that the dividing pressure is related to the soils’ character,especially dependent on the air content. The explosion temperature has a certain conduction time and rise time in soft soil, and it rises more slowly than that in the air. Besides, relevant theories are used to compute the pressure and temperature.The calculated results are compared with the measured results. The conclusions of this paper provide a reference for the design of underground civil air defense engineering and ground compaction engineering in coastal soft soil area.