Fault knowledge mapping can quickly find one or some fault causes related to the fault phenomenon and lock the scope of investigation through the method of knowledge quiz or sub-map matching. For the mechanics, when the query results in multiple fault causes, each fault cause has the same probability, and it is impossible to formulate targeted maintenance measures. Therefore, this paper introduces the fuzzy Bayesian inference algorithm to take advantage of its causal inference logic in order to realize the optimization of aero-engine fault diagnosis strategy.