Abstract: sing the method of an artificial neural network, a real-time algorithm is proposed for the fault detection of a liquid propellant rocket engine in this paper. Neural network used for fault detection can approximate the working process of rocket engine by the way of nonlinear identification technology,and it can also generate an identified residual signal that contains the engine fault message at the same time. If the identified residual signal becomes bigger than a given threshold, then there occurs an engine fault. Neural network can be trained for off-lime condition in all flight or for on-line condition in the stabilizing process of the rocket engine running. The experimental research has shown that the artificial neural network has been successful employed in the fault detection of the large turbo-pump liquid rocket engine.