Iron tower is used as holder on high voltage transmission line normally, especially for 110~1000KV transmission line. Hot rolled curb angle is frequently adopted and connected to form truss structure by bolt. There are also few poles, which are processed to section by steel tube. Connect two ends with flange plate and bolt to form steel tube tower. Cold bended-wall rolled section may also be used as tower material. Hot-galvanizing is always applied for anti-atmospheric-corrosion. Based on structure type and stress characteristic, iron tower may be divided as stayed tower, self-supporting tower and large crossing tower.