Abstract: Based on the conventional integrate expression approach, a modified time-domain formulation method is proposed for the calculation of aerodynamic forces acting on bridge girders. Both the effects of aerodynamic derivatives on self-excited forces and the partial correlated effects of aerodynamic forces over the chord of the girder section are taken into consideration in the present method by certain calibration techniques and appropriate aerodynamic admittance functions. The proposed method represents an important breakthrough in restrictions of the quasi-steady hypothesis, and the problems induced by the direct employment of such hypothesis without modification are solved to some extent in this study. The method remains its simplicity and straightforwardness as compared with the complicated theory employed in the non-integrate expressions for aerodynamic forces on bridge girders. Buffeting responses of a unique long-span cable-stayed bridge with three towers are investigated by the proposed method. The numerical results are agreeable with the wind tunnel test results on the whole, indicating the method developed in this paper is correct and practicable.