【Objective】 To construct a fuzzy ontology of maize disease knowledge representation and reasoning model.【Method】Using data from sources to construct fuzzy ontologies，which were combined with fuzzy theory to construct the disease diagnosis model by ontology technology. 【Result and conclusion】The theory of fuzzy was introduced into the description of ontology form and the shortcoming of an ontology representing the narrow defined knowledge only was overcame by this model. Combining the formal definition of ontology with the indeterminacy presentation advantage of the theory of fuzzy, the robustness of maize expert system for diagnosis and treatment of diseases was increased. Meanwhile，this model improved the accuracy of diagnosis and treatment of maize diseases and presented a new knowledge representation reference for other agricultural production expert systems.