Experimental investigations of supersonic laminar/turbulent flow over a compression ramp are carried out in a Mach 3.0 wind tunnel, the angles of ramp are 25 degrees and 28 degrees. Fine structures of holistic flow field and local regions are visualized via nanoparticle-tracer based planar laser scattering (NPLS) technique, some typical flow structures such as boundary layer, shear layer, separation shock, recirculation zone and reattachment shock are visible clearly, and the wall pressure coefficient of laminar flow is measured. The angle of separation shock and reattachment shock, the development of boundary layer after reattachment are measured by time-averaged flow field structures. The analyses of time-relevant NPLS images reveal the spatio temporal evolution characteristics of flow field. The experimental results indicate that when the ramp angle is 25 degrees, a typical separation appearing in the supersonic laminar flow with boundary layer increases and is converted into turbulence quickly, at the same time, a shock is induced by developing boundary layer; K-H vortexes, shear layer and compression waves arise in the flow field. But the supersonic turbulent flow does not show separation, and the turbulent boundary layer always adhers to the wall. When the ramp angle is 28 degrees, the range of recirculation zone expanded obviously in supersonic laminar flow which is separated further, induces shock and separation shock moves upstream, reattachment shock moves downstream. Therefore the structures of separated region is complicated. By comparison with laminar flow, the range of recirculation zone in supersonic turbulent flow is obviously small, boundary layer increases slowly, and there are not any induced shock, K-H vortexes, compression waves in the flow field. The structures of separated region is simple, but the strength of separation shock is much stronger.