Abstract: Periodical wake vortices may cause vortex induced vibration of a long span bridge, the vortexinduced aerodynamic force produced by vortices is partial correlation along the span. Based on Scanlan's semi-empirical linear model, the correlation of vortex-induced aerodynamic force along span is studied. The inner-relation of force spectrum from 2D to 3D is found by Fourier transform, and reduced factor of vortex induced response between 2D to 3D is defined, and the methodology for applying modeling test results into prototype is discussed. Validity of proposed theory is proved by different scale sectional models and full aeroelastic model wind tunnel tests.