PURPOSE: To provide a nozzle fixation structure for a ramjet which can realize reduction of weight of the ramjet, reduction of a cost, and improvement of reliability.

CONSTITUTION: A ram nozzle 10 is provided with a gas communication port 10c which is communicated with an inner space of a ramjet 1 and opened to a clamp 13 which fixes a booster nozzle 11 to the ram nozzle 10 and an accumulator 10d which is communicated with the gas communication port 10c. A piston 15 and a compression coil spring 16 are arranged in the gas communication port 10c for introducing combustion gas into the accumulator 10d when the internal pressure of the ramjet is hight, and injecting high pressure gas to the side of the clamp 13 from the accumulator 10d when the internal pressure of the ramjet is lowering.