Abstract: According to the requirements of study on fault diagnosis of large-scale liquid rocket propulsion systems, an inverse-problem model on fault diagnosis has been established and an algorithm to solve the model has also been put forward in this paper. The method is based on genetic algorithm (GA). After investigation on characteristics and difficulties of inverse-problems on fault diagnosis, the algorithm used for solving the inverse-problems is studied emphatically. Finally, an application example obtained from inverse-problem model by genetic algorithm is also illustrated, which demonstrates that the above-mentioned inverse-problem model and algorithm are sound and effective.