In order to provide a reference value for aerodynamic lift acting on twin parallel box girders in actual engineering projects， twin parallel box girders with different aspect ratios are selected. The lift coefficients under different wind attack angles and spacings are measured through pressure measurement wind tunnel test of rigid model， which are compared with those of single box girder. The interference effect of downstream box girder is expressed quantitatively by introducing interference factors. The results show that the interference effect on the aerodynamic lift is slight for upstream box girder and obvious for downstream box girder. Under most positive wind attack angles， the interference effect on the aerodynamic lift for the downstream box girder is mainly manifested as a reducing effect. Under negative wind attack angles， the lift on the downstream box girder is downward. The downward lift increases with increasing wind attack angles and decreasing spacing and aspect ratio.