Abstract: According to an aquarium test, an experimental method was proposed to measure shock waves in the near field of an underwater explosion. The axial scanning photographs were obtained and analyzed digitally. The shock front pressure along the axle of the charge was gained from the scanning trace of shock wave by using the Rankine-Hugoniot relation, and was extrapolated to the initial pressure of shock wave. The axial pressure damping of the cylindrical TNT charges in the near field was computed by the code LS-DYNA, and the initial pressure of shock wave was measured by manganin gauges. The experimental result is consistent with the theoretical calculation, and the near-field axial pressure damping of the cylindrical TNT charges follows an exponential function.