Abstract: Shock/turbulent boundary layer interaction(STBLI) in a M_∞=3.0 supersonic compression ramp flow are studied using a spatial large eddy simulation method. At upstream, flat plate transition and developed turbulent boundary layer are simulated in which Shock/turbulent boundary layer interaction shows at the ramp. Analysis on mechanism of turbulent boundary layer/shock interaction indicates that linear unstable disturbance leads transition rapidly. In the process of STBLI, average separation range of the ramp is smaller than that in the laminar flow. However, extent of the separation shows different characteristics in different span-wise positions due to high velocity strip and low velocity strip.