The shock wave generated by high-voltage pulse discharges in liquid has been widely used in industrial applications. In this paper, an integrated experimental platform of underwater pulse discharges is established, a needle-plate electrodes system with the gap distance of 10 mm is used. The influence of voltage polarity on the process, morphology and physical characteristics of streamer development are discussed, based on the analysis of energy transfer process, the influence of voltage polarity on the shock intensity is studied. The results show that for the subsonic streamer, the use of negative polarity voltage can significantly improve the energy conversion efficiency of the shock wave. For the positive polarity, the supersonic streamer mode can significantly reduce the energy loss of the prebreakdown process, increase the rate of expansion of the plasma channel, and obtain a higher intensity of shock wave. Using the negative polarity voltage, or controlling the voltage of the positive polarity to make streamers develop in the supersonic streamer mode, can significantly improve the intensity of the shock wave.