The influence of electric pulse parameters on spark discharge characteristics in water was studied. A solid-state repetitive nanosecond pulse power supply with adjustable parameters was adopted. The discharge load was a pin-plate structure placed in water (the distance between the pin and the plate set to 1 mm). The experiment was carried out under low repetitive frequency conditions (approximately 5 Hz). The characteristics of pulse discharge in water were obtained by monitoring discharge parameters, taking high-speed shadow images, collecting optical emission spectrum, and measuring sound pressure. The evolution of pulse discharge with different parameters and its influence on acoustic and spectral characteristics were also obtained. When the energy storage on the order of a few joules after the initial discharge channel was formed between the two electrodes, the circuit current rose to approximately 10 A within a few hundred ns, followed by a rapid and then slow decline with a duration of 50-60 μs. It is found that the preset pulse width has a great influence on the spark discharge characteristics. Under short pulse width conditions, the discharge channel will be cut off by the solid-state switch of the power supply. Under long pulse width conditions, the discharge channel becomes unstable in the late stage and even interrupts the arc,and the secondary discharge appears in bubbles. The radiation spectra reveal more information. With the increase of pulse width, the intensity of the characteristic spectral lines increased, but no new spectral lines were observed. This indicates that the number of active particles increased, and their types remain the same.The channel electron density is estimated on the order of 10¹⁸ cm^-3. The characteristic width of the pulse sound wave produced by a short pulse (＜150 μs) is 110-150 μs. However, when the pulse width continues to increase, the sound wave pulse width does not continue to increase but remains at 150 μs. It is hoped that this research has a certain reference value for studying the mechanism of small energy spark discharge, and provides ideas for the applications of underwater acoustics, liquid phase plasma and other fields.