Abstract: The pulse detonation rocket engine(PDRE) with variable cross-section was investigated using kerosene as fuel and oxygen as oxidizer at the equivalence ratio 1.0 and the working frequency of 8Hz, including constant cross-section engine, divergent engine, convergent engine, divergent-convergent engine and convergent-divergent engine. The effect of cross-section change on the propagation process of detonation in the pulse detonation rocket engine was studied. We could also obtain the effect of cross-section change on the average thrust of engines.