Abstract: The flow control effect of Ramp-VG array(ramp vortex generator array, RVGA) on the supersonic mixing layer was studied via the nano-tracer-based planar laser scattering(NPLS) technique at a convective Mach number of 0.17. By comparing the NPLS images of the supersonic mixing layer without control and with RVGA control, it is found that the flow velocity in the mixing layer increases by 5%~15% under the control state, and the mean wavelength of K-H instability vortices decreases by 5%~30%, while the length of laminar flow increases by 12.8% at location y_1/2 (the tip of the ramp). The flow development process in the supersonic mixing layer was studied combined with the fractal theory. It is found that the value of fractal dimension obviously changes with RVGA control, namely that the value increases at location y₀(the tip of the RVGA′s notch) and decreases at location y_1/2. The experimental results prove that the RVGA can improve the energy distribution in the supersonic mixing layer, which thereby achieves the goals of delaying transition, altering mixing intensity, increasing flow velocity and decreasing anisotropy of vortices.