Supporting towers are the main load-bearing structures of the feed support system of FAST. They comprise of 6 steel pipe towers, each of which is more than 100m high and the highest is 173.5m. The 6 towers stand around the depression in a 600m-in-diameter circle with a uniformly-spaced and axi symmetric arrangement. They can bear alternating cable tension up to 400kN imposed by the cable robot. The 6 towers are named after clock according to their positions, namely 1H, 3H, 5H, 7H, 9H and 11H respectively.