Large scale superconducting magnets are planned to be used in diverse areas of science projects which need high. magnetic field level around 10T. As superfluid helium (HeII) near atmospheric pressure can reach a lower temperature near 2K and has far better thermal conductivity and larger heat capacity, it would improve the performance of the magnets considerably. As the coolant of superconducting magnets serves also as an electrical insulation medium, it is necessary to study the dielectric strength of HeII. In this study, breakdown characteristics of pressurized superfluid HeII were investigated experimentally in uniform and non-uniform electric fields. The breakdown field strength mea sured under uniform field condition increases with a shorter gap length and pressure. With a positive point electrode, glow corona discharge is observed beyond a critical gap length. At a lower temperature, the positive corona appears with a shorter gap length and the breakdown voltage increases. No corona discharge is observed with a negative point electrode. The breakdown voltage is always higher with the negative point than positive one. No apparent change in the breakdown characteristics is observed during phase transition from normal liquid helium to superfluid helium.