This paper presents demonstration experiments on magnetohydrodynamic (MHD) boundary layer control in M=1.5 supersonic flow. In this study, Cs seeded Ar gas was used to operate DC discharge at low voltage to reduce the Joule heating and to obtain high MHD interaction parameter for boundary layer control that was the ratio of the Lorentz force in boundary layer to the skin friction. The effects of the electromotive force have been observed in electrical current distributions along the flow direction, DC voltage dependency of the magnetic field strength, and DC discharge emission distribution in the boundary layer. These results and the plasma potential distribution measurement with floating probes indicated the DC discharge was operated at low loading factor of about 1.5 while the MHD interaction parameter for boundary layer control was in range from 5 to 8. Modification of the supersonic boundary layer was detected by a high speed response Pitot tube as the modification of the Mach number, because the energy input to the supersonic flow was restricted and the MHD interaction was strong enough to modify the boundary layer flow. Because oblique shock-wave in front of a ramp was influenced by upstream boundary layer flow, the oblique shock wave location was investigated by increasing or reducing the momentum of boundary layer flow by the accelerating Lorentz force or the Joule heating. The oblique shock wave location in front of 10 or 20 deg ramp was moved toward downstream by applying the accelerating Lorentz force and moved to upstream by operating DC discharge without the magnetic field.