To　investigate　dynamic　flow　instabilities　of　hydrocarbon　fuel　in　thermal　protection　structure　of　the　scramjet,　experiment　was　conducted　at　the　pressure　of　1.5-3.0　MPa,　heat　flux　of　190-250　kMfm(-2),　and　the　charge　pressure　at　the　surge　tank　of　0.5-1.0　MPa.　Three　main　types　of　dynamic　flow　instabilities,　pressure　drop　oscillation,　density　wave　oscillation,　and　thermal　oscillation　took　place　during　some　experimental　conditions.　The　influence　of　hydraulic　characteristics　of　the　test　loop　on　dynamic　flow　instabilities　was　discussed.　It　was　found　that　dynamic　flow　instabilities　were　mainly　affected　by　the　hydraulic　characteristics　of　the　test　loop　rather　than　the　heating　section.　Pressure　drop　oscillation　with　large　fluctuation　amplitude　and　long　period　occurred　in　the　negative　slope　region　of　the　pressure　drop　curve.　Density　wave　oscillation　appeared　in　the　positive　slope　region　with　low　flow　rate.　The　fluctuation　amplitude　and　period　of　density　wave　oscillation　were　much　smaller　than　those　of　pressure　drop　oscillation.　Dynamic　flow　instabilities　were　more　intense　at　lower　pressure　and　higher　heat　flux.　The　oscillation　region　was　independent　of　the　compressible　volume.　However,　a　large　compressible　volume　could　promote　the　fluctuation　amplitude　of　both　inlet　mass　flow　rate　and　outlet　fuel　temperature.