Abstract: Electrohydraulic discharge plasma rock breaking is a novel, safe, controllable, green, and environmentally friendly rock breaking technology. The attenuation characteristics of the electrohydraulic shock wave are the key issues that need to be clarified in the application of the technology of discharge plasma in liquid. In this study, constructed is a test platform composed of an electrohydraulic discharge device, a plugging and electrode integrated component, a water tank, a discharge voltage and current testing system, and a shock wave testing system in water. Tested are the discharge voltage, the discharge current and, the electrohydraulic shock wave pressure time history curves under the working conditions of the electrode spacing of 5 mm-30 mm and of the charging voltage of 6 kV-10 kV. Analyzed is the influence of electrode spacing and of charging voltage on the attenuation of the electrohydraulic shock wave pressure peak with a propagation distance. The research results show that the electrohydraulic shock wave pressure peak increases first and then decreases with the increase of electrode spacing, showing a non-monotonic characteristic, while it is positively correlated with the charging voltage. The influence of electrode spacing and of charging voltage is related to the energy deposition characteristics of the plasma channel. The electrohydraulic shock wave pressure peak attenuates with the propagation distance in a power function. The influence of electrode spacing and of charging voltage on the attenuation rate of electrohydraulic shock wave is small, while the influence on its initial intensity is large. A power function attenuation model of the electrohydraulic shock wave attenuation with a propagation distance is proposed. Through fitting analysis, the attenuation index is determined to be −0.76. The initial amplitude parameter k of the shock wave increases first and then decreases with the increase of electrode spacing, and increases monotonically with the increase of charging voltage. It increases approximately linearly with the increase of plasma channel energy deposition power. The research results can provide an experimental basis for the parameter design and engineering application of the technology of discharge plasma in liquid.