When we use the strain gauge in the high temperature water, lowering of insulation resistance between test material and gauge is the matter. The lowering makes the measurement unstable and is the primary factor of an error. This study devises the waterproofing method in empirically that has the best insulating property in the hot water($100^{circ}C$), In this way, we can reach the conclusion that on the condition of a few hours we can measure precisely in the high temperature like normal temperature.