The conduction current is believed as important factor for evaluation of materials. Generally, the electric field of insulation for direct current (DC) was dependent on the conduction characteristics. However, the conduction current is affected by noise generated from various conditions. The purpose of this paper is to establish a measurement conditions of the conduction current that minimize noise. In the study, the conduction current was measured three times according to electric field for polypropylene (PP) model cable. We analyzed the measurement conditions of the conduction current on noise according to applied electric field. As a result, the deviation of the conduction current was calculated as 6.0% under 25kV/mm. It was proved that the influence of noise was the least under this condition. We are proposed a measurement condition of 25kV/mm to diagnosis HVDC PP power cables.