The high strength INVAR alloy has been used in equipment in which temperature changes because its superior thermal characteristics. High temperature condition could induce change of its microstructure which can cause mechanical deformation. This research focuses on developing a characteristics of INVAR alloy. We studied two different type of INVAR alloy (Fe-Ni-V and Fe-Ni-Mo) and analyzed the heat effect on the change of microstructure and mechanical characterisitics were studied using metallographic examination such as XRD, TEM and EBSD technique and mechanical test such as tensile, hardness and twisting test.