As the basic study of the passive control of the shock oscillation, steady pseudo shock in the rectangular ducts with the porous wall and the bypass system was investigated experimentally and numerically. The expriments were carried out in a blow-down supersonic wind tunnel at a free stream Mach number of 2.0. Numerical simulations were made with the 2-D compressible Navier Stokes code. In sloving the equations, 2nd-order accurate Harten-Yee's upwind TVD scheme and κ-ε turbulence model were used. It is shown that the boundary layer thickness under the first shock wave of the pseudo-shock is controlled by the passive control method without noticeable changes of the pseudo-shock strcuture. But the total pressure loss downstream of the pseudo-shock is reduced by this method. And the effects of some parameters influencing the passive control method are studied numerically.