Failure cases are very important for failure analysis. So how to deduce the failure mode of a new failure case based on existed failure cases will be discussed in this file. Firstly, according to the collection of large accident case, summarized how to deduce the failure features and failure information of each failure modes may have. Then identify the possibilities of the new failure case belong to each kind of existing failure mode, using the fuzzy identification method put forward in this paper. And then judge which failure mode the failure case is most likely belongs to.