A partial discharge(PD) measurement is a very effective method to assess the insulation condition of high-voltage machines. It is necessary that the life time of the on-line PD measurement sensor is assessed. Therefore, the electrical life time assessment method of ceramic element was reviewed in order to estimate the life time of the on-line PD measurement sensor. The samples were prepared according to the reviewed method and were tested at 8kV, 9kV and 10kV. Based on the obtained results, the life time constant is shown above 59. Also, it is assumed that the estimated life time constant can be used to anticipate the life time and to assess the conformity of the on-line PD measurement sensor.