Abstract: The Paper details the applications of fault diagnosis techniques of foreign manned spacecraft as well as its development process, and highlights the expert system techniques. The fault diagnosis for foreign manned spacecraft ranged from the 1960s' simple condition monitoring, the 1970s' algorithm-based diagnosis to the 1980s' knowledge-based intelligent diagnosis. On the other hand, the paper also presents two fault diagnosis expert systems developed by NASA for space shuttle main engine turbopump and space station freedom power system and comprehensively analyses the characteristics of fault diagnosis expert systems in space field, and then discusses the future work.