Abstract: A box-wing can significantly reduce the induced drag relative to a conventional monoplane, and its smooth lift distribution is beneficial to reduce the transonic wave drag, but aerodynamic interference between dual wings is the principal problem needed to be solved for a transonic box-wing aircraft. In order to improve the transonic aerodynamic interference characteristics, how the geometric parameters affect aerodynamic performance of both positive and negative staggered layout at M=0.75 was numerically investigated, a supercritical airfoil RAE2822 was used for dual wings. Results show that increasing the longitudinal distance can reduce the aerodynamic interference between dual wings and increase the lift-to-drag ratio up to the noninterference case. For a negative staggered layout, which the front wing is under the rear wing, a high lift-to-drag ratio close to noninterference value can be achieved when the longitudinal distance is 1.5 times the upper wing chord length. At this distance, the gap has little effect on the lift-to-drag ratio, without decalage and reducing chord ratio is conducive. The negative staggered layout is confirmed to be more conducive for enhancing the lift-to-drag cha-racteristics.