Abstract: The concept of tandem wing with rear wing dihedral configuration was proposed for future high maneuver small aircraft. The Navier-Stokes(N-S) equations in a 3D coordinate system was solved with the finite volume method. A <i<k-ω</i< shear stress transport(SST) two-equation turbulent model was also applied to make numerical simulation for 4 comparison models with different rear wing dihedral angle. Combined with theoretical analysis and experimental verification of the prototype, the characteristics of the aerodynamic interference between the wings, and the effects of the rear wing dihedral on the flight performance were investigated. The result shows that rear wing dihedral can avoid the airflow interference caused by front, and ensure the cruise stability at small angle of attack. Meanwhile the adverse impact of continue interference between front wing and rear wing was analyzed, and some solutions were put forward. The study indicates that the rear wing dihedral can play the same role as the vertical tail to enhance the lateral and directional stability, and the structure weight and aerodynamic resistance caused by wetted area can be reduced by eliminating the vertical tail.