Abstract: In view of the complexity of the disease and pest problem,fuzzy reasoning method was presented in the agriculture disease and pest diagnosis expert system, including disease and pest introduction, symptoms,database of weights. Considering both positive and negative effects of the disease and pest symptoms on the diagnosis results, threshold was used to choose information given by users. Weighted Euclidean distance method was introduced to calculate the comparability. Effective diagnosis results and reliabilities were given out. Besides,users were granted with certain authorities to modify database. Finally ,the reasoning process was illustrated.

Key words: fuzzy reasoning, weighted Euclidean distance method, expert system, reliability