Abstract: Planar Laser Induced Fluorescence (PLIF) can be used to visualize the flame structure with high temporal and spatial resolution and investigate the mechanism of supersonic combustion. In this paper, OH-PLIF and CH-PLIF techniques were used to study the flame structure in supersonic combustion. The cavity-stabilized reaction zone structure of the three streamwise sections and two spanwise sections in a supersonic combustor was obtained by using the OH-PLIF technique. The experimental results show that the combustion occurs in the inner cavity and the OH radicals are distributed symmetrically along the central axis at a low global equivalence ratio. The OH radicals are primarily distributed at two-side-wall of the combustor and the location of the flame is higher than that of the cavity at a high equivalence ratio. The heat-release structure of the cavity-stabilized flame was observed by the CH-PLIF technique. It is found that the heat-release zone is highly wrinkled and distorted in the supersonic combustion and it is distributed in a narrower region than the reaction zone.