Making the oyster mushroom as acommodity business to society and farmers easy andfleksible. But diseases and pests can attack the oyster mushroom cultivation making difficult forfarmers to identify and preserve. The development of technology can be used for identification. This system is made by using the Naïve Bayes classifier method as a method to classify all datasymptoms of disease and pests that will attack the oyster mushroom, Naïve Bayes method is widely used as a method of classifying the data that known as data mining. Naïve Bayes methodare implemented in the expert systemis expected to facilitate the mushroom farmers in the process of identifying disease that attacks mushroom. With the expert system, it is expected to facilitate the work of farmers in identifying diseases and pests oyster mushrooms