The effect of flap and slat riggings on the multi-element airfoil was investigated numerically. The compressible Navier-Stokes equations were solved by the finite-volume method. Spalart-Allmaras (S-A) turbulence model was used. The effects of flap and slat riggings on lift coefficients and pressure coefficients were provided. The validation of computation agreed well with the experimental results. The computations on the effect of flap and slat riggings shows that lift coefficient has an optimum with every design parameter. With proper flap and slat riggings, the adverse pressure gradient and the separation on the backward wing section could be suppressed, and the wake from forward wing section does not mix with the boundary layer of backward wing section. So the performance of the airfoil can be improved.