To construct a cross-strait bridge with a center span exceeding 2000 m, such as the bridges in Ise Bay, the Kitan Strait, Tokyo Bay, or the Second Kanmon Bridge, the design and the construction must be developed so as to minimize the construction cost at water depths exceeding 100 m. We propose a low-cost construction method using"hybrid main tower structure, jacket and steel-pipe-pile foundation." The structure consists of a hybrid main tower using CFT (Concrete Filled Tube), a jacket in the sea, and a steel-pipe-pile foundation in the sea bed, rather than the conventional construction of main tower and lay-down caisson, which is expensive and difficult to construct for marine bridges. We studied the bearing capacity of the steel-pipe-pile, the strength of the joint between the jacket and piles, and the ultimate capacity of the main tower. We also calculated the seismic safety of the overall structure, ensuring the structure's potential and safety.