The operation of KTX in Korea has launched since 2004, which brought about a great change in railroad industry. We have acquired lots of great know-hows, especially in railroad construction and operation field. Therefore, we have been building up numerous operation skills until now. However, it was necessary to investigate some of the equipment based on our own environment because the high speed train system were totally imported. In case of Toughened Glass Stem Insulator, it was totally new type in domestic. This paper introduces estimation method and result in three different field aspect, such as an electrical field, a physical field, and environmental circumstances. First, in case of an electrical field, amplitude and a number of time for switching surge voltage data were collected. Second, in case of a physical field, amplitude and trend of vibration in to the insulator were examined. Finally, in case of environmental circumstances, flying possibility of gravel and ice clod were investigated. Also shrink and expend characteristic according to temperature were reviewed. Through this basic data, suitability for Toughened Glass Stem Insulator using in domestic high speed railway have been accumulated and estimated.