1. A computer-implemented method for system component failure diagnosis, the computer-implemented method comprising: responsive to a computer determining that a number of component failure cases corresponding to a complex system stored in a historical diagnosis database is less than a pre-defined threshold number of component failure cases, predicting, by the computer, a system component failure root cause using a rule-based reasoning method; and calculating, by the computer, a diagnosis accuracy of the system component failure root cause predicted by the rule-based reasoning method based on historical data corresponding to the complex system stored in the historical diagnosis database.