Body rotating bridges are mostly rotation system in balance, whose gravity center are basically located in the rotation axis of turntable. In order to ensure bridges’ swivel construction successfully accomplished, the structural center of gravity should be made clear before the rotation. In the past, the structural center of gravity was usually ascertained in the method of mathematics, but the tedious calculation couldn’t get results with enough accuracy. In this paper, structural gravity center of cable-stayed bridge is calculated in the method of CAD and finite element, whose process and result are proved handy and accurate calculation. Taking Sui Fenhe cable-stayed bridge as an example, its theoretical eccentricity is 1.3cm.