Abstract: The three dimensional effects of hypersonic laminar separated flow induced by the compression corner were investigated numerically. The three dimensional compressible laminar Navier-Stokes equations were solved by finite volume method with Roe's two-order spatial scheme and multi-block structured grids. It shows that the numerical simulation results of spatial shock wave structures were in good agreement with the schlieren photos obtained by experiment before. The numerical pressure distribution along three different lines and the experimental data in the shock wave/boundary layer interaction flowfields were respectively compared and analyzed. And a low pressure zone was found beside the 3D wedge. The numerical results indicate that the lowest pressure is at the zone where swept by the secondary vortex which is initiated from the ramp corner. In addition, the low pressure in wake flow of 3D wedge would partly effect the upstream flow field through the subsonic boundary layer.