The effects of injection and main flow conditions on the turbulent structure produced by a gaseous sonic transverse injection into a supersonic airstream were investigated. The turbulent structure of mixing was characterized by the single-time two-point spatial correlations based on the concentration fluctuation measured with the acetone planar laser-induced fluorescence (acetone PLIF). Results revealed several geometrical characteristics such as shape, size, and appearance intervals of the large-scale vortex structures. The correlation maps indicated that organized large-scale structures appeared in the upper region of the jet irrespective of the injection conditions. Velocity field resulted from the mainstream condition dominated the turbulent behavior. The injection with higher compressibility condition showed more stable structures and slower development of the turbulent structures due to suppression of instability growth. As a result of that, the higher compressibility case showed slower mixing rate.