The present study describes the numerical investigations concerning the injection and mixing phenomena of a secondary gaseous jet through a transverse slot nozzle in a wall into a supersonic stream which is uniform outside of a turbulent boundary layer. The numerical investigations are performed by solving the fully two-dimensional Navier-Stokes equations using Roe`s FDS method and the 2nd order implicit TVD scheme. The results show that bow shock wave/turbulent boundary layer interaction induced the boundary layer separation in front of the injection. In interacting flow, when the total pressure ratio or width of injector increased, the interaction region and shock structure considerably changed.