Because forest fire can give a serious damage to overhead conductors, the thorough understanding about aging behavior of burned conductor is very important in maintaining the transmission line safely. Therefore, a systematic investigation was carried out by heating method. As the heating temperature increases, drastic change of tensile strength of Al wire due to the softening of Al wire occurred. When Al wire is exposed to the flame(about $800;^{circ}C$) during only 13 seconds, the remained tensile strength of Al wire showed under 90 %. The detailed results will be given in the text.