Abstract: A similar new bridge is planed to be built adjacently to an existed single-tower cable-stayed bridge which has double inclined cable planes with a main span length of 310m. Aerodynamic coefficients interference effects of the existed bridge on the adjacent new one are investigated with wind tunnel tests, the extent of interference is described with the aerodynamic interference factors, and CFD computation of wind flow is carried out at some flow cases to explore the interference mechanisms. The results show that the existed bridge could remarkably affect the aerodynamic coefficients of the new bridge. The variation patterns of the interference factors with the change of attack angles appear quite similar for both operation and construction states of the new bridge. The interference factor of the drag coefficient increases with the increase of the absolute value of attack angles while the interference factor of lift coefficient decreases with the increase of attack angles. However, it is noted that no obvious variation pattern for the interference factor of torque coefficient can be observed.