A rocket engine with an improved solid fuel segment mainly comprises a combustion chamber, a solid fuel segment installed in the combustion chamber, and an oxidizer injector installed at one end of the combustion chamber. The solid fuel segment surrounds and forms a trajectory to allow the oxidizer injector to inject oxidizer into the trajectory, in particular, on the solid fuel segment is formed with a plurality of protrusions, between the each two protrusions are defined a recess, a flame holding hot-gas region is formed between the protrusion and the recess, so as to produce eddy current in the flame holding hot-gas region when the propellant mixture is burned inside the trajectory, such that the whole solid fuel segment can produce even regression rate and high combustion efficiency.