On the basis of direct-connect scramjet test system simulating flight Mach number 4, different injection modes were compared to study the influence of flame stability on fixed geometry dual-mode scramjet combustor fueled with liquid kerosene and ignited with torch-model ignition. It is indicated that the flame is difficult to stabilize in the flow condition of lower total pressure and total temperature. It is also indicated that the flame stability in dual-mode scramjet combustor is greatly influenced by the injection mode of kerosene.