The　high-velocity　oxygen　fuel　thermal　spray　system　can　provide　a　hypersonic　flowing　environment　in　which　the　temperature,　pressure,　and　speed　are　all　sufficiently　high　to　represent　a　more　realistic　environment　of　hypersonic　vehicles　than　that　produced　by　traditional　oxyacetylene　flame.　In　this　work,　the　ablation　resistance　of　C/C　and　C/C-SiC　composites　under　hypersonic　flowing　propane　flame　is　investigated,　and　the　microstructure　evolution　during　the　ablation　process　is　examined.　It　is　found　that　different　ablation　regions　are　formed　depending　on　the　size,　and　the　distributions　of　temperature　and　pressure　on　the　front　surface　of　the　samples.　With　the　increase　of　ablation　time,　a　dense　and　continuous　oxide　layer　forms,　which　acts　as　a　barrier　to　prevent　the　interaction　of　oxidizing　gases　and　composites,　and　can　also　block　the　conducted　heat　and　resist　high　temperature　scouring　of　hypersonic　flowing　flame.　In　addition,　a　numerical　analysis　is　performed　using　ANSYS　Fluent　software　to　investigate　the　fields　of　velocity,　pressure,　and　temperature　on　the　front　surface　and　around　the　carbon　fibers　of　the　sample.　The　simulation　results　further　demonstrate　the　evolution　of　microstructures　of　C/C　and　C/C-SiC　composites.