A size-dependent gradient method is used to study the Mie scattering visualization of the compressible turbulent mixing layers at two convective Mach numbers Mc = 0.107 and 0.474 in order to reveal multi-scale structures. Coherent vortices and inclined wavy structures are clearly visualized by applying the method. Similarity between the grey-level and the velocity fluctuations is discovered with the spectral analysis. These results suggest a way to capture turbulent structures from scalar fields.