Abstract: High-voltage pulse fracturing technology is based on the electro-hydraulic effect principle, where strong shock wave generated by the discharge of water pulse creates cracks in the rock. It has become a hot research subject in the field of rock fracturing. This paper sets up two types of current source modules applied to the water discharge, the single and the double current source modules. And the electrodes voltage and current waveforms of the modules are explored by the needle electrodes at different discharge voltage with 1mm electrode gap. The experimental results show that at the same discharge voltage without any load, the double module generates greater discharge current, resulting in higher instantaneous power at the time of discharge; while for underwater discharge, there is a great randomness in the pre-breakdown time of the water gaps. The minimum and maximum standard deviations of the pre-breakdown time for the single module are 0. 285 ms and 1. 481 ms respectively, while for the double module, the minimum and maximum deviations are 0. 369 ms and 0. 703 ms. From the overall trend, the higher the discharge voltage is, the shorter the pre-breakdown time will be: the average time of the double module varies from 2. 686 ms at 1300 V to 1. 036 ms at 1800 V.