Linear stability analysis was utilized to investigate the stability characteristics of a supersonic boundary/mixing layer confluent flow. The basis flow was designed as a mixing layer with hyperbolic-tangent profile over a compressible boundary layer with similar solution profile. Special attention was paid to the influence of wall distance and convective Mach number on the stability of this field

of which adiabatic wall condition was used. The distance from mixing layer center to the wall ranged from 5 to 15 times boundary layer thickness

and the convective Mach number varied from 0.6 to 1.2. It was found that novel multi-unstable modes existed in the confluent flow and the dominant modes showed different manners with varying wall distance and convective Mach number.