Abstract: In order to shorten the mean fault isolation time,the fault isolation strategy based on dynamic entropy search is proposed in this paper on the basis of entropy-directed algorithm and entropy-indirected algorithm.The strategy takes the maximum dynamic-entropy of the system for account to select tests and establishes fault isolation decision tree using ergodic search on the centre of dynamic entropy.It is showed by algorithm example that the strategy in this paper needs less tests and mean fault isolation time than entropy-directed algorithm and entropy-indirected algorithm.