Abstract: Under the condition of hypersonic flight, the temperature of the air flowentering the combustion chamber of ramjet is very high. A large fraction ofthe available reactive heat of air and fuel of such high temperature will betransferred to dissociation energy of the products. When the burnt gases runover the exhaust nozzle with limited length, the dissociation energy can notbe released fully. As a result, the thrust of ramjet drops and can not meet theneeds of propulsion requirement for hypersonic flight. This effect is termed``hypersonic barrier''. For surmounting the``hypersonic barrier'', sometentative ideas are proposed. Under the condition of preserving the breathingand burning modes of existent ramjet, the catalysis is utilized to promotethe recombination of dissociation compositions during expansion in nozzle.Thus the thrust of the ramjet may be increased to the extent that therequirements of hypersonic propulsion can be met.