Shock wave is generated by the electro-hydraulic effect in high-voltage pulsed discharge technology, and local hole reaming is built in downhole. Finally, pedestal piles with different diameters are formed via cement injection. This paper describes the high-voltage pulse discharge technique about the pile forming mechanism by hole bottom reaming, the pile forming process and the effect on the pile diameter, studies the work of shock wave and vapor expansion pressure on pile diameter. The field experiment is carried out by using a newly introduced high-voltage pulse discharge device, the results show that the theoretical formula results are in good agreement with the experimental results.