In this paper, thermal and mechanical properties of electric epoxy with water aging were discussed. We made elastic epoxy specimen adding a ratio of 0〔phr〕20〔phr〕, 35〔phr〕 and 53〔phr〕 with modifier to existing epoxy. We studied mechanical property of elastic resin after absorption in water from 0 to 484 hours. As a result, diffusion factor of elastic epoxy showed 20-21${ imes}$10$^{-4}$ $ extrm{mm}^2$/s and general epoxy showed 9.5${ imes}$10$^{-4}$ $ extrm{mm}^2$/s. Elastic property increased linearly according to addiction and decreased according to water absorption. Tensile strength was reduced according to addition. It was affected by water absorption of micro-void of elastic epoxy. Hardness inclined to decrease after increasing according to absorbed time. In water-absorption state, it was experimented a change of heat flow by temperature of elastic epoxy and change of thermal expansion coefficient. DSC (Differential Scanning Calorimetry) and TMA (Thermomechanical Analysis) equipments were used to measure Tg. A temperature ringe of DSC was from -0($^{circ}C$) to 200($^{circ}C$). One of TMA was from -0($^{circ}C$) to 350($^{circ}C$). In addition, we investigated structural analysis of water absorbed specimen using SEM (Scanning Electron Microscope).