Abstract: Perturbation mixing enhancement effects are evaluatedfor supersonic mixing layers by NPLS flow visualization technique. Someexperiments are carried out to optimize the parameters of the disturbances.The images reveal that the mixing layers are sensitive to the disturbanceswithin the splitter plate. 2D disturbances advance the unstable position ofthe mixing layer and thicken it to enhance mixing, while 3D disturbancespromote flow 3D characteristic to enhance mixing by inducing streamwisevortexes and spanwise convolution. The mixing-enhancement effect of 3Ddisturbances is better than that of 2D disturbances. Although the tape islocated in the sub-boundary layer, the shock wave is inevitable in thesupersonic flow. These Mach waves are the main reason for the loss of totalpressure in this mixing-enhancement method.