The invention provides an air sac component of a steel tube for a water transportation extra-high pressure steel tube tower, which comprises air sacs in pairwise distribution, wherein each pair of air sacs are mutually and fixed connected, and are in detachable connection with the steel tube to support the floatation of the steel tube; and each air sac comprises an air sac body, an inflation part and a pull ring respectively arranged at the two sides of the air sac body, and a connecting piece for fixing the steel tube. Relative to the prior art, the air sac component provided by the invention adopts air sacs so as to provide buoyancy for steel tubes in the water transportation process, avoids the mode that plugging flanges are arranged at the two ends of each steel tube to provide buoyancy for the steel tube in the prior art, is in no need of processing the plugging flanges with various specifications, and lowers the transportation cost of the extra-high pressure steel tube tower.