Complex knowledge base question and answer oriented query graph generation method and system

The invention relates to a query graph generation method and system oriented to complex knowledge base questions and answers. The method comprises the steps that according to the semantic similarity between a target question and historical questions, the historical questions ranked in the top are screened out from historical cases; forming a case candidate relation set by the relations in the standard query graph corresponding to the screened historical questions; on the basis of the case candidate relation set, a search type semantic analysis method is adopted to generate a query graph; and converting the query graph into an executable query statement according to a grammar rule of a knowledge base query statement, and executing query on the knowledge base to obtain an answer to the target question. According to the method for remarkably reducing the retrieval space in the reasoning process through the historical cases, candidate relations obtained through retrieval are pre-screened, and the question answeri